US2458558A - Radiotelephone equipment - Google Patents

Description

E G. e. BRADLEY 2,458,558

RADIO TELEPHONE EQUIPMENT Jan. 11, 1949.

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Filed July 26, 1946 To ENVENTOR 13, 655: f 5AOLEX Jan. 11, 1949. g. BRADLEY 2,458,558-

RADIO TELEPHONE EQUIPMENT Filed July 26, 1946 2 Sheets-Shae 2 law) 64 (o/V7201. flan-E Pan 5e In;

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Hy lNVENTOR meqe lie/amen ATTORN EY Patented Jan. 11, 1949 2,458,558 RADIOTELEPHONE EQUIPMENT George G. Bradley, Great Neck, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application July 26, 1946, Serial No. 686,265

17 Claims.

This invention relates to-radio-telephone equipment.

It has particular application in two-way radiotelephone service where it is required to operate between ships and on ship-to-shore service. The invention is well adapted to the communication needs of ships which ply our inland water ways, such as rivers and lakes.

My invention is exemplified in certain radiotelephone equipment which has been built and successfully tested and which, as a specific embodiment, comprises transmitting circuits pretuned to as many as six radio frequency channels and six radio receivers, also pre-tuned.

The main body of the equipment, including the radio circuits, is usually located at some point remote from the operators station. It is therefore required that it be completely operated by remote control. Preferably on ship-board two telephone stations are installed, one, say, in the pilot house, and the other in the radio operators cabin or captains quarters. The different transmitting circuits and receivers are adjusted for service on assigned carrier waves, such as have been provided by the Federal Communications Commission for use on the Mississippi River and its tributaries, or on the Great Lakes. The frequency range is within the limits of 2000 to 9000 kilocycles. The power output of the transmitter is preferably in the 75 watt range. The equipment has been proven satisfactory for service over distances as great as 800 miles. In pla and answering calls a frequency channel is usually chosen among six that are available whereby optimum conditions of communication may be chosen according to the time of day and with respect to the distance between stations.

Among the many noteworthy objects of my invention are the following, which are considered the more important:

1. To provide a flexibly operable two-way radio communication system especially adapted for use between ships and on ship-to-shore service on inland waterways, such as rivers and lakes.

2. To provide radio-telephone equipment the transmitter of which is serviceable with a minimum of delay for answering a call, and which will give satisfactory service over distances up to 800 miles.

3. To provide equipment for radio-telephone communication selectively on any one of a plurality of I frequency channels certain of which wouldbe allocated in the 4, 6 and/or 8 megacycle bands for daytime service, other channels being preferably allocated in the 2 to 3 megacycle band for general service over land and fresh water; for example, between vessels which navigate the Mississippi River and its tributaries.

4. To provide radio-telephone equipment for use on ship-board whereby the placing of outgoing calls and the answering of incoming calls may be expeditiously handled at either of two stations, the main part of the installation being remotely situated.

5. To provide for continuous monitoring of incoming calls by means of a plurality of receivers, say six, which are operable in a stand-by condition; each receiver being tuned to a difierent frequency channel and their outputs being impressed upon aloud speaker or a selective .rcall responsive device which responds to specific code signals and causes an alarm to be sounded upon reception of its code number.

6. To provide specialized switching devices in a multi-channel radio-telephone system whereby during a telephone conversation over a selected radio frequency channel all receivers are momentarily silenced While talking; all receivers of unused channels are completely silenced until the conversation is ended; and whereby the unused one of two telephone stations is rendered incapable of operation to in any way interfere with or intercept a communication carried on from the station momentarily in use.

My invention will now be described in more detail, reference being made to the accompanying drawings in which a single circuit diagram is shown by Figs. 1 and 2. Fig. 215 to be placed on the right'hand side of Fig. 1, so that the conductors which appear to run from one figure to the other maybe placed in registry.

Referring first to Fig. 1, this figure in its entirety represents a control unit A for one telephone station. This control unit comprises a hook switch IOI whereon a hand-set I02 may be hung when not in use. The control unit also includes a loud speaker I03 which is principally used for continuous monitoring of incoming calls on the three medium or low frequency channels. A bell I04 is also provided in the control unit. As will be explained hereinafter, this bell is sounded by relay operation whenever a selective ringer I05 responds to code signals. This selective ringer is preferably connected through a ringer amplifier I06 to the output terminals of three receivers D, E and F which are tuned to the higher frequencies.

A channel selector switch having a multiplicity of ganged contact wipers and cooperating contacts' wafers, lettered a to 1 inclusive, is provided for use of the equipment on any of six radio frequency channels, numbered I to 6 inclusive. The gang switch also has a position for stand-by operation, so that continuous monitoring of incoming calls may be had on any of the six receivers ,three of which would impress their calls upon the loud speaker and the other three of which would be responsive by way of soundingthe alarm through the selective ringer I and bell I04.

The control unit A shown in Fig. 1 may be the sole telephone station on board, but preferably two such units are provided. In Fig. 2, therefore I have shown as a block diagramv asecond control unit B the components of which will be understood to be exact duplicates of what is provided in control unit A.

The radio equipment is housed in a single cabinet which may be located wherever spacev can be conveniently found on shipboard. This cabinet contains the radio circuits of the transmit,- ters and receivers, also certain switching devices which are remotely controlled from the control stations. Furthermore it houses the selective ringer I05. and a motor-generator for the transmitter power supply. The motor-generator is not shown, but it will be understood that it requires starting mechanism for which a control circuit 209 is provided. The receivers are operated from the ships D. C. power line. The motor-generator is operated only when carrying on a conversation and provides anode, screen and negative biasing voltages for the transmitter tubes.

In order to provide for exclusive control of, the, equipment from either one of the two control units A and B, I provide certain relay equipment in a junction box. This relay equipment in combination with the switchingdevices of the control units is described and claimed in a co-pending application filed by myself jointly with Harry F; Mohr Ser. No. 679,344 on June. 26, 1946'. Other than terminals, the junction box contains only the relays 60I, 602 and 604, the first two relays beingparallel-connected.

The control unit The remote control unit with which the handset I02 is associated is provided with a switch I01 having connections 8| and 82 to-a similar switch at control unit B. Either of these switches may be used to connect or disconnect the ships 115.-volt D. C. power line +L to or from the telephone equipment. A pilot lamp I08 lights upwhen the ships line is connected to. the receivers. Switch I09A or I093 is used for selecting the particular control unit- A or- B respectively w-hereat a callis to be placed or answered. Assuming that thehand-set at control unit B has not been lifted switch I09A operates (before lifting'the hand set)v to. transfer telephone service from control unit. B to control unit A. Switch I I0 is; provided for choosing between loud speaker and, earphone receoption. The hand-set, I02 is provided with. a push-button I I I- which must be depressed when talking. In the hand-set is aground connection common to the terminals of the earphone, the microphone and the push-button. The pushbutton circuit may be traced from ground through conductor 30, contacts of relay 60-2, the coil. of relay- I12 and thenceto the negative terminal-C of the transmitter power supply, in which the +C' is ground potential.

Thev relay II'2 operates two movable contacts b, and e. which. are associated with front contactsa, and cl respectively, and contact e normally rests.

4 against back contact 1. Several functions ar performed as folows: (1) Closure of contacts at and e supplies negative line potential (-L) to the winding of relay II4 on the other side of which +L potential is supplied through normally closed contacts b and c of relay I I3. Relay I I4 operates, therefore, as a slave to relay I I2. (2) The breaking of contacts e and f on relay II2 opens the cathode and gain control circuits of all the receivers, thus silencing the same. (3) Closure of contacts a. and b on relay I I2 in series with contacts f and g on relay II4 removes a blocking potential from the cathodes of the oscillator and the power amplifier tubes for keying the transmitter carrier on. This is accomplished by effectively short-circuiting resistor I22 (4700 ohms) through the very low value resistor I57 (5 ohms). Normally (with the push-button not depressed) the carrier wave is not propagated because of a positive potential applied to the cathodes just mentioned. This positive potential results from the voltage drop (approximately volts)- through resistor I22 which carries a bleedercurrent derived from a voltage divider (not shown but indicated by terminal T) connected across the anode potential source terminals in the motor generator, the negative terminal being grounded. Thus a potential drop exists in resistor I 5l which is; sufficient to energize the microphone.

Function (4) of the relay H2 is: to open the circuit between the. negative line terminal -L and all of the receiver gain control circuits, thus silencing the receivers while talking. This circuit when normally closed may be traced from relay contacts II2e, -f through relay contacts I I'3fe-e, through conductor I'I8, through branched rheostat. elements H5, H6 and II "I to certain contacts of the channel selector which connect with gain control circuits 43, 44 and 45 leading to the cathodes of R. F. and I. F. amplifier stages (not shown) in the low frequency receivers A, B and C. The connections to corresponding cathodes in receivers D, E and F may also be traced from conductor II'8 through other contacts of the channel selector and through conductors #0, M and 42 to the high frequency receivers. I

Relay II4' when operated as a slave to relay I I2 performs further functions thus:

(1') Closure of its contacts ab. connects the antenna I23 to conductor H4 which receives output signals from the transmitter I25 by way of one of the wafers inv a motor-driven gang, switch I26. This switch in its. entirety serves to select. the frequency of the carrier wave. Its, novel features are described. and claimed in my co-pending application Ser. No. 679,343 filed June 26, 1946.,

Function (2). of relay I- I4 is to open the circuit. at its contacts c-b so as to disconnect the antenna from conductor I, 2;'I having branches to each of the signal input terminals of the six receivers. During talking periods, therefore, no signal can. reach the receivers. Function (3) is carried, out by closure of contacts de, thus grounding the input circuits of the receivers: for the purpose. of noise suppression. Function (4); isfulfilled by closure of contacts I I4J'--g andismerely contributory to the performance (as above described) of function (3) of relay II2, that is, to close the microphone circuit. One virtue in the double make; and break of this circuit is, to minimize key clicks. The. operation, of; relay H14, is delayed by a, few microsseconds. with respect. to that of re.- lay II2.

The channel selector switch Although this switch was briefly mentioned in the foregoing description its functions will now be more fully explained. Practical considerations, as well as the authorized assignments of radio frequency channels for Mississippi River shipping service dictated that the switch wipers be moved to positions 3, 4 or 5 for communication on the respective low frequency channels, and that positions 1, 2 and 6 be used when communicating on the relatively high frequency channels.

Position is used for maintaining stand-by conditions in which the output circuits of the three low frequency receivers A, B and C are connected through conductor 39, switch wafer 71. and thence through contacts of the hook switch II to the loud speaker I I33. Also the output circuits of the high frequency receivers D, E and F are connected through conductor 38 and switch wafer i and thence through conductor 31 to the ringer amplifier I06.

The gain control circuits for each of the receivers F, E, D, C, B and A is brought out individually through one of the conductors 40 to 45 inclusive and is connected to a wiper On one of the wafers f, e, d, c, b and a respectively.

A gang-controlled rheostat comprises adjustable resistors H5, H6 and II! by which the volume of three receivers can be manually set. As shown in Fig. 1 resistor H5 at the left hand terminal is connected to different stationary contacts on wafers 1, c, b, a, e and d. Resistor H6 is connected to one contact at the 0-position on wafer c and resistor II"! is connected only to the contact at the 0-position on wafer b. The right hand terminals of these three rheostat resistors are connected in common through conductor H3 to movable contact 6 on relay H3, thence through back contacts 7 of the two relays H3 and H2 and through movable contact II 2e to the L terminal which supplies cathode potential to certain amplifier stages in all of the receivers. Preferably these are the radio frequency and the first intermediate frequency amplifier stages.

The gain control circuits for the high frequency receivers D, E and F are connectable directly to conductor H8 when the channel selector switch is set to any of the positions 0, 3, 4 or 5. Thus for stand-by conditions and when using any one of the low frequency channels for a communication the high frequency receivers are all operated at full gain.

In switch position 1 the gain control circuit for receiver D may be traced through conductor 42, wafer d, resistor H5, conductor H8 and thence through relay contacts to the ,L terminal. Silencing of all the other receivers is then accomplished by opening their gain control cir cuits. So switch position 1 is useful for communicating on the channel to which receiver D is tuned.

In switch position 2 the gain control circuit for receiver E is connected through conductor 4|, and wafer e to resistor H5 and is completed as described in the preceding paragraph. At the same time all other receivers are silenced. Likewise the gain control circuit for receiver F is connected through conductor 49 and wafer f to'resistor H5 when switch position 6 is selected. All other gain control circuits are likewise open for that channel selection.

In switch positions 3, 4 and 5 the respective gain control circuits of receivers A, B and Care 6. singly connected in each case. to rheostat H5 while the gain control circuits of receivers D, E and F are connected directly to conductor H8 and thence to the L supply terminal. Hence, as previously mentioned, the high frequency receivers are operated at full gain and their output circuits are connected to the selective ringer for monitoring purposes during periods when any one of the low frequency channels is being separately monitored.

Switch wafer g has its stationary contacts I to 6 inclusive connected individually to pilot lamps I20 for clearly indicating the setting of the channel selector switch when it is moved away from the 0-position. The Wiper on wafer g feeds current to a selected lamp from a 6-volt source upon closure of contacts dand e when the hand-set I02 is lifted from its hook IDI.

Three of the pilot lamps IZII which stand in channel positions 1, 2 and 6 respectively are also connected through conductors 35, 34 and 33 respectively to contacts in the selective ringer unit I05. Unit I05 is arranged and adapted to close these circuits selectively when it is actuated by the proper sequence of audio frequency call signals; In practice the signal pulses are of 600 and 1500 cycle modulation which are alternated at a rate of 4 to 5 /2 cycles per second. The selector set on each ship may be arranged to respond to any one of a number of five-digit codes, so that the selective calling of any one of a group of stations operating on the same carrier frequency is possible. The terminating pulses of the call signalsignify the communication channel to be used, and by illuminating a particular one of the pilot lamps I20 the answering party is enabled to turn his channel selector switch to the proper position for answering the call on any one of the high frequency channels.

Switch wafer 7 on the channel selector switch has connections through a cable to individual contacts of a motor-driven rotary gang switch IZBat the main equipment unit. The details of construction and operation of switch I26 are not herein given since they are covered in my copending application Ser. No. 679,343 filed June 26, 1946. The setting of switch I26 is accomplished under control of a relay H3 which is in circuit with a selected conductor in cable 5!] and operates to keep the armature of motor I28 energized until the setting of switch I26 corresponds with that of the wiper on wafer 7' of the channel selector switch. The gang switch I26 performs numerous functions, such as selecting the proper radio frequency tuning elements in the transmitting equipment and connecting the proper output circuit to conductor I24 for feeding outgoing signals to the antenna I23. The gear train through which the motor I23 drives the gang switch I26 includes preferably a worm. reducing gear I29 and a Geneva movement I30.

In order to listen to a particular receiver the channel selector switch must be set to the desired channel. This connects the cathodes of the selected receiver to the volume control rheostat I I5 and connects the output of this receiver to the loud speaker circuit. When one of the receivers A, B- or C is selected the high frequency receivers D, E and F remain connected to the selective ringer, as hereinabove explained. And when one of the high frequency receivers is selected for a communication, then all'of the non-selected re ce-ivers are silenced by opening their gain control circuits. This arrangement has been found to meet the practical requirements of two-way radio telephone service in the Mississippi River and Great Lakes regions.

Transmitter circuits The six sets of pretu-ned transmitter circuits are preferably of atypewherein carrier power in the '7'5-watt range is generated by a crystal controlled tuned anode circuit oscillator. A separate quartz crystal and oscillator. anode tank circult is provided for each transmitting channel. These circuits are switched by wafers on the gang switch I26.

By means of another wafer on the gang switch I26 the selected, tuned transmitter unit is connected to a number of parallel-connected power amplifier stages. Audio frequency output from the modulator unit I 2I is applied to the screen grids and anodes of those power amplifier stages. The modulate-d output is then coupled to one of six sets of antenna tuning circuits connections being made through still another wafer of the motor-driven gang switch. Finally, the antenna conductor I247 is connected to the selected antenna tuning circuit, through one more wafer of the gang switch in unit I26. All these details of transmitter circuit switching may readily be worked out for different transmitter circuit designs by those skilled in the art. For purposes of this: disclosure, therefore, it is preferred to symbolize by block diagram the transmitter circuits I25 and the gang switch l'26 for channel frequency selection. It will be understood, however, that for the practical operation of my invention it is essential that the motor-driven gang switch- I2'6 be capable of automatic adjustment to any position corresponding to positions 1 to 6 inclusive in the manually operable channel selector switch at the control unit. Furthermore, since the motor-driven switch I26 is capable of rotation in one direction from any previous setting to. any desired new setting, it matters not where it is set at the time of shutting down the transmitter and of turning the manually operable switch to the stand-by position. In fact, the motor-driven gang switch has no stand-by position, for it needs none. But itv always assumes a position corresponding to positions 1 to 6 inclusive of the manually operable gang, switch, the latter exercising its control through its wafer 7'.

The earphone, microphone, modulator and pushbutton The cord I3I for the hand set H32 contains separate conductors for the microphone, the earphone and. the push-button III. Also for these three elements there is a common return conductor connected to ground.

When using the earphone the output from one of the receivers is brought through one or the other of the conductors 38-39 to the wiper on channel selector switch Wafer h and thence through conductor I32, through closed contacts I) and a of hook switch IIH, and manual switch IIEl, this last being thrown to make connection with the earphone. The return circuit is through ground to a grounded terminal of the secondary winding (not shown) on the receiver output transformer. While listening the antenna I23 is connected through normally closed contacts b and o of relay I I4 to all of the receiver input terminals in parallel.

The microphone is connected. through a circuit which may be traced from ground through the microphone, thence through the modulator unit I2I, and through a 5. ohm resistor I51 to ground. By closing contacts f and g of b and a of relay II2v a. suitable voltage drop is produced through resistor I5! which constitutes the D. C. supply to the microphone, as heretofore indicated.

The push-button I I I- is connected through conductor 30. to the winding of relay I I2 and thence to the C terminal of the transmitter power supply. The +C terminal is grounded. The transfer functions of relays H2 and IM as controlled by the push button I I I have already been described. It should here be noted, however, that the receivers can all be silenced in two Ways-one by operation of the push-button-controlled relay II2 which opens its contacts e and f; the other by operation of relay I I3 which opens its contacts e and ,f. In the latter case the receivers are silenced during the movement of the channel selector switch I26 from one to another position. These four relay contacts just mentioned when normally closed complete the receiver gain control circuits to the L power supply terminaL, as hereinabove set forth.

The hoolc switch When the hand-set I02 is lifted from, its hook IllI contacts of the latter operate as follows: Contacts b and 0 open to silence the loud speaker. If loud speaker operation is preferred to earphone reception while engaged in a conversation, then switch H0 may be thrown to the proper position for that purpose. Closure of switch-hook contacts a and b connects the receiver output to the movable contact on switch I-IIl.

Closure of switch-hook contacts at and e supplies potential froma +6-volt source terminal to the wiper on channel selector switch wafer 9 so as to light up one of the channel indicating pilot lamps I220. The negative terminal of this 6-volt source is the same as the -L terminal. So the return circuit common to all the lamps I20 joins that of the bell I64 and includes conductor -32, contact ,1 on relay 602 which is directly connected to the -L terminal.

Closure of switch-hook contacts 1 and g connects conductors 9 and 36 to conductor 46, whereby +L potential is supplied (1) through switch water 9' and conductor 50 to relay II 3 for operating the motor-driven channel selector switch I26; (2) through conductor 46 to terminal 209 on the starter coil of the motor-generator; and (3) through conductor 46 to the Winding of a so-called lock-out relay 604- in the junction box. The function of this relay will presently be explained. The three branch circuits closed by switch-hook contacts f and g. are all returned to. the L line terminal.

The junction boa:

The junction box contains terminal boards for the inter-connecting cables which are necessary for remote control of the. radio equipment from either of two remote control stations. The junction box also contains the necessary relays B01, 602 and 604 for switchingthe control circuits from one remote control unit to the other.

As shown in Figure 2 the relays EDI and 602 have their windings connected in parallel and each relay operates nine movable contacts most of which engage with both front and back stationary contacts. Practically it is preferred to use three relays in place of relays GUI: and 602 in order that the spring load of each relay coil may not be excessive. The assignment of contact springs to the different circuits is immaterial aside from the fact that the front contacts, with one exception, must all lead to components in the control unit A shown in Figure 1 and the back contacts lead to corresponding components in the control unit B. To avoid unnecessary tracing of circuits the connections between the back contacts and control unit B have not been shown.

Normally control unit B is maintained in control of the system, relays EM, 602 and 603 being unenergized. Control may be switched to control unit A by momentarily closing switch I09A on that unit. This energizes relays 60I and 602, the circuit for which may be traced from the +L terminal at switch I01 in station A through one of the conductors 80 or BI, switch I01 at station B, conductor 9, switch I09A (momentarily closed), conductor 48, contacts and b of relay 604, conductor 80 and through the coils of relays SM and 602 to the L terminal.

The relay circuit just traced is locked up by closure of contact e and its front contact on relay 602, this locking circuit extending temporarily (until the hand-set I02 is lifted from its hook) from live conductor 9 to conductor I9, thence through contacts of switch I09B, and conductor 80 to the coils of relays SM and 602.

Now the exclusive use of control unit A for the period of a telephone conversation may be insured by lifting the hand-set thereat. This energizes the lock-out relay 604 in the following manner: Live conductor 9 connects through contact d of relay 602 to conductor 36, thence through contacts g and f of switch hook IOI, conductor 46, contact 0 of relay 602 and the coil of relay 604 to the L terminal. This circuit is also branched to the starter terminal 209 so that the motor generator may be started up for supplying power to the transmitter.

The lock-out function of relay 604 is eifected this way: Closure of its contacts e and d makes direct connection between the +L terminal and conductor 9, and since relays 602 and 604 are both energized the +L potential traverses contacte of relay 602, conductor 19, contacts a and b of relay 604 and conductor 80 to the coils of relays GM and 602. Note that contacts a and b of relay 604 are in shunt with switch I09B in control unit B, so that the opening of that switch cannot result in loss of control at the control unit A so long as its hook-switch is up. Furthermore, the switches I01 are effectively shunted by contacts d and e on relay 604, thus preventing the power from being shut off at the unused control unit.

When control unit B is to be used, the operator will first see that the power switch I01 iscorrectly set for lighting the Power on pilot lamp I08. If no sound is heard in his speaker he operates switch I09B momentarily in order to break the locking circuit that held relays SM and 602 energized by previous use of control unit A. Control. is then returned to control unit B, provided the operator at control unit A has hung Now the lifting of the hand-set at control unit B results in energizing the look-out relay 604 through circuits which are like those previously described in reference to control unit A, but which traverse the back contacts associated with movable contacts d and c on relay 602. Note that contact 0 of relay 604 is connected through conductor48 to a contact of switch 109A at control 10 unit A. Therefore, the opening of contacts b and con relay 604 establishes exclusive control at'control unit B. Again, while relay 604 is energized the power switches-I0? at the two control units are shorted by closure of contacts d and e on relay 604. So the two switches I07 and I09A at control unit A are both disabled during a tele-' phone conversation carried on at control unit B.

Complete privacy of use of either control unit is insured by means of the transfer switch contacts of relays GM and 602. Thus, considering relay 60! when it is not energized, the receiver output circuits 38 and'39 are carried to the manually operated channel selector switch 220 at control unit B. So, also with'respect to the gain control circuits 40 to 45 inclusive. And conductor 31 which leads to the input terminal of the ringer amplifier is broughtback from control unit B through the back contact nearest the core of relay 60L" r Considering relay 602 when it is not energized, its back contacts which are associated with movable contacts a and dare connected to the microphone and push-button respectively on the hand-set I02B at control unit'B. Back contacts associated with movable contacts 17, c, and I lead exclusively to the hook switch and bell (not shown) at control unit 'B. Also the pilot lamps for channels I, 2 and 6 at the control unit B are connected to the selective ringer I05 only when movable contacts g, h and i on relay 602 rest against their associated back contacts.

All of the conditions set forth in the two preceding paragraphs are modified by the energization of relays 60I and 602 so that complete privacy is obtained at control unit A whenever desired.

Operation In the preferred embodiment of my invention the operating procedure for monitoring and answering calls is as follows:

(1) Turn the power switch I01 so that the pilot lamp I08 glows.

(2) Allow 15 seconds for receiver tubes to warm (3) .Turn the channel selector switch to Stand-by, the (l-position. Adjust the receiver volume control clockwise as far as possible. Atmosphere noise and incoming calls on channels 3, 4 and 5 will be heard from the loud speaker. Incoming calls on channels I, 2 and 6 will actuate the automatic ringer I05. When the bell I04 rings the incoming call will cause one of the pilot lights I20 to be illuminated corresponding to the channel number to be used in answering the call.

(4) If no sound isheard from the loud speaker, operate the control unit selector switch .I09A or I09B momentarily and release. This shifts reception to the adjacent speaker.

(5) When the channel selector switch is on channel 3, 4 or Efincoming calls on channels I, 2 and "6 will still actuate the selective ringer. Listening on channels I, 2 or 6 will disable the selective ringer.

(6) Remove the hand-set I02 from its hook and thereby cause the motor-generator to be started up. The motor-generator comes up to full speed in approximately three seconds. The warming-up period for the transmitter tubes is scarcely more than this, so that, for practical purposes the transmitter is ready to go on the air as soon as one has listened for a reasonable time to make sure of a clear channel.

11 Closure ofswitch-hook contacts i and g causes a restoring voltage to :be applied to the stepping magnet (not shown) in the code selector, whereby the code wheel is restored to normal and the ringing of the bell 404 ceases.

(7) If it is desired to listen on a single channel to the exclusion of all others, the channel selector should be turned to the desired channel number and the'volume control adjusted to a satisfactory level either for loud speaker use or ear-phone use.

The calling procedure is relatively simple:

(1) Turn the channel selector switch to the desired channel number and listen for one minute to make sure that the channel is not in use.

(2) Set the switch H to the desired position for use of either the loud speaker or the earphone.

(3) Remove the hand-set H12 from the hook I DI and wait for the channel pilot lamp to light up.

(4) To talk, hold down the push-button- Ill. Release to listen to the other party.

It is, of course, important to replace the hand set on the hook after completing a call. The channel selector switch should also be turned to stand-by (0) position and the receiver volume adjusted to a sufficiently high level so that the next incoming call will be clearly heard on the loud speaker.

For service in the Mississippi River region the radio frequency channels atpresent assigned and their uses are as follows:

connect a gain control circuit to the corresponding amplifier stage of the selected receiving unit through said volume regulator, (2) to connect the same selected receiving unit to said audible responsive device, and (3) to disconnect the gain control circuits from the remainingreceiving units, thereby to silence the same.

2. In a selective switching arrangement for a radio-telephon installation, a multiple-position gang switch the wipers of which have a stand-by position and to any position corresponding to a selected communication channel, and, connected thereto, a plurality of receiving units each differently tuned to one of the channel frequencies to be used, a selective ringer responsive to code signals when received on certain of said channels, an audible responsive device, a volume regulator and gain control circuits individual to certain amplifier stages in each of said receiving units, said gang switch being operable in a stand-by position: (1) to connect a number of said gain control circuits through said volume regulator to the corresponding amplifier stages, (2) to connect the corresponding receiving units to said audible responsive device, and '(3) to connect the remaining Frequency 2206 2738 To communicate with New Orleans only. Ship to Ship Various Shore Stations.

Short Distance-Day-time Coverage Long Distance-Night Long Distance Day & Night Day-time only The frequency assignments as given in the above table are those now authorized for transmitting from Mississippi River ships. Reception is at the same frequencies except on channel 3, since New Orleans transmits at a frequency of 2598 kc.

For the Great Lakes region and for other radiomarine services the frequency allocations would be difierent, of course, so that no limitations are to be imposed upon the uses of my invention for transmission and reception of radio communications at any frequencies whatsoever.

It will be understood by those skilled in the art that various modifications of my invention may be made without departing from its patentable scope.

I claim:

1. In a selective switching arrangement for a radio-telephone installation, a multiple-position gang switch the wipers of which have selected positions each corresponding to a selected communication channel, a plurality of receiving units each having one amplifier stage and each differently tuned to one of the channel frequencies to be used, an audible responsive device, volume regulators, and gain control circuits one of each corresponding to one amplifier stage in each of said receiving units, said gang switch being 'connected to said amplifier stages, said response device, and said volume regulators and gain control circuits, said gang switch being operable: (l) to the channel frequencies to be used, a selective ringer responsive to code signals when received on certain of said channels, an audible responsive device, a volume regulator and gain control circuits individual to certain amplifier stages in each of said receiving units, said gang switch being operable in certain of its channel selecting positions: (1) to connect the gain control circuit to the selected receiving unit through said volume regulator; (2) to connect the same receiving unit to said audible responsive device; (3) to disconnect the gain control circuits of certain others of said receiving units, thereby to silence the same; and (4) to connect the remaining receiving units at full gain to "said selective ringer.

4. In a selective switching arrangement for a radio-telephone installation, a multiple position gang switch the wipers of which have different selective positions corresponding to selected radio frequency channels, including "certain channels in a high frequency band and other channels in a low frequency band, an audible responsive device, a selective ringer, a plurality of receivers, adjustable gain control circuits each corresponding to certain amplifier stages in each of said plurality of receivers, said receivers being individually tuned to different ones of saiclchannels and thereby including low frequency and high frequency receivers each having output terminals and circuit means connected to the wipers and stationary contacts of said gang switch and also connected to: (a) said responsive device, (In) said ringer, (G) the adjustable portions of said gain control circuit arrangement, and (d) the output terminals of said receivers, said means being operable in accordance with the setting of said switch wipers: (1) to connect the output terminals of said low frequency receivers to said audible responsive device, (2) to connect the gain control circuit to the selected receiver, (3) to disconnect thegain control circuits from the remaining low frequency receivers, and (4) to connect the output terminals of said high frequency receivers to said selective ringer while maintaining the corresponding gain control circuits operable at full gain.

5. Ina selective switching arrangement for a radio-telephone installation, a multiple position gang switch the wipers of which have different selective positions corresponding to selected radio frequency channels including certain channels in a high frequency band and other channels in a band of relatively low frequency, an audible responsive device, a selective ringer, adjustable gain control circuits individual to certain amplifier stages in each of a plurality of receivers, said receivers being individually tuned to different ones of said channels and thereby including low frequency and high frequency receivers each having output terminals, and circuit means connected to A the wipers and stationary contacts of said gang switch and also connected to said responsive device, said ringer, the adjustable portions of said gain control circuits, and the output terminals of said receivers, said means being operable in accordance with the setting of the switch wipers:

(1) to connect the output terminals of said high frequency receivers to said audible responsive device, (2) to connect the gain control circuit to the corresponding selected amplifier stage, and v(3) to disconnect the gain control circuits from the remaining receivers, thereby to silence the same during atelephone conversation.

6. In a selective switching arrangement for a radio-telephone installation, a multiple position gang switch the wipers of which have selectively difierent positions corresponding to selected radio frequency channels including certain channels in a high frequency band and other channels in a band of relatively low frequency, and, connected to said switch, an audible responsive device, a selective ringer, adjustable gain control circuits individual to certain amplifier stages in each of a plurality of receivers, said receivers being individually tuned to diiferent ones of said channels and thereby including low frequency and high frequency receivers each having output terminals, and circuit means connected to the wipers and stationary contacts of said gang switch and also connected to said responsive device, said ringer, the adjustable portions of said gain control circuits, and the output terminals nel selectorswitch for usein a radio telephone system, said switch comprising a plurality of contact wafers each having a movable contact wiper and an. associated array of stationary contacts, all wipers being gang-controlled, and, connected to said switch, a plurality of receivers each tuned to adifferent carrier frequency and each having an output circuit and a gain control circuit, a manually operable volume regulator of the rheo stat type, a listening device and a selective ringer unit, said switch being'operable under stand-by conditions (1) to connect the output circuits of certain receivers to said listening device and simultaneously connect the corresponding gain control circuits to its receiver through said volume regulator, and (2) to simultaneously connect the output circuits of the remaining reif-said receivers, said means being operable in ceivers to said selective ringer unit, with the gain control circuits for these remaining receivers being shunted across said volume regulator, and said switch having other positions inwhich the output circuit of a selected receiver is connected. to said listening device and the corresponding gain control circuit is connected to the selected each comprising a hand-set, a channel selector switch to selectively choose one of said circuits when connected to said transmitter receiver, and remote-control switching means, and a junction box containing relays connected to and subject to control from said remote control units, said remote control switching means being connected to said circuits,- said hand-set, and said channel selector switch and operable: (1) to connect the channel selector switch at a particular one of said control units to said transmitter receiver, and (2) to actuate at least two of the relays in 7 said junction box, thereby to cause the other control unit to be disconnected from the receiver.

10. In a radio telephone system, a transmitterreceiver installation comprising pre-tuned radio frequency circuits for selective use on a plurality of different channels, a motor-generator for energizing the circuits of the transmitter, a direct current source for energizing the receiver circuits and for driving said motor-generator, two remote control units each comprising a hand-set, a channel selector switch and remote control switching means, and a junction box containing relays subject to control from one of said control units whereat control is'preempted, said remote control'switching means being operable: 1) to coin nect the direct current source to said generator and to-connect said direct current source to said receiver circuits, (2) to connect said pre-tuned circuits to the channel selector switch at the prempting control unit, and (3) to actuate at least two of the relays in said junction box, thereby to cause the unused control unit to be disconnected frequency channels in one housing and two control units remotely situated with respect toeach other and to said housing, audible responsive means at each of said control units and connected selectively one at a time to said receiving apparatus, a gang switch at each control unit and constituting means at times operable for selecting a desired radio frequency channel of two-way communication for use a said transmitting and receiving apparatus, control unit disabling means, and relay means operable under control of switching devices at a preempting control unit to connect said disabling means to the other control unit thereby locking out and disabling the other control unit to prevent the same from exercising control and interfering with a telephonev conversation which is commenced at said preempting control unit.

12. A system according to claim 11 and including means under control of said gang switch and operable by setting the same to a stand-by position to connect a plurality of said radio frequency channels to said receiving apparatus whereby a certain plurality of radio frequency channels are simultaneously monitored by said receiving apparatus and to connect the receiving apparatus to the audible responsive means whereby the audible responsive means receives the receiving apparatus output and is audibly responsive thereto.

13. A radio telephone system comprising a remote control unit and transmitting and receiving apparatus including components thereof which are pre-tuned for operation on different radio frequency channels, said apparatus bein separately housed with respect to said remote control unit, a manually operable gang switch in said control unit, said switch having a standby position connecting aplurality of components simultaneously in circuit in said receiving apparatus for elfecting multiple channel monitoring of incoming signals by said receiving apparatus, and having single channel selecting positions connecting selected components in circuit in said apparatus for obtaining single channel operation of the transmitting and receiving apparatus, a motor-driven gang switch in the housing of said transmitting and receiving apparatus, electrical means for causing the motor-driven gang switch to assume any one of a plurality of single channel positions corresponding to that to which the manually operable gang switch is concurrently set, said motor-driven gang switch constituting means connecting a single selected component in circuit in said transmitting apparatus for causing said transmitting apparatus to be tuned to a desired channel frequency corresponding to the selected receiver frequency, means connected to the manual gang switch and operable by selectively setting the manual gang switch, to a single channel position for conditioning the receiving apparatus to translate incoming signals only as received on said desired channel frequency, and means controlled by the two gang switches for suppressing the operation of transmitting and receiving components which are tuned to non-selected channel frequencies.

14. A system in accordance with claim 13 and including an additional remote control unit similar to the first remote control unit and selective means for obtaining exclusive use of either of the two remote control units while looking out control of the transmitting and receiving apparatus by the non-selected remote control unit.

15. A radio telephone system comprising a re- 16.. mote control unit and receiving apparatus including components thereof which are pre-tuned for operation on different radio frequency channels, said apparatus being separately housed with respect to said remote control unit, a manually operable gang switch in said control unit, said switch havin a stand-by position to connect a plurality of components in said apparatus for efiecting multiple channel monitoring of incoming signals by said receiving apparatus, and having other positions to connect a selected component in said apparatus to provide reception on a selected radio frequency channel, output circuits and gain control circuits for each of said differcntly tuned receiving apparatus components, said output and gain control circuits having connections completed by said manually operable gang switch in selected positions thereof whereby said apparatus effectively receives single channel voice reception and the concurrent reception of incoming selective code signals by others of said receiving apparatus components.

16. A radio telephone system comprising transmitting and receiving apparatus arranged for two-way service on any one of a plurality of radio frequency channels and having means for monitoring simultaneously a plurality of channels for incoming signals, a pair of remote control units each including a microphone-earphone hand-set, and control switches for establishing different circuit conditions in said system, a push-button on each hand-set, relay means subject to control by said push-button for conditionin said transmitting apparatus to radiate a signal modulated by a microphone of a selected hand-set, said relay means being at the same time effective for silencing the receiving apparatus, other relay means automatically operable to disconnect the other control unit until the hand-set which is in service is hung up, and channel selecting means operable at times to condition the transmitting and receiving apparatus for single channel twoway communication and at other times for multiple channel monitoring of incoming signals.

17. A system according to claim 16 and including a selective ringer and a loud speaker, circuits to connect certain channel-tuned units of said receiving apparatus and said loud speaker, other circuits to connect the ringer with the remaining units of said receiving apparatus; said channel selecting means being effective to make all of said circuit connections, and means for controlling the volume of response in. the loud speaker.

GEORGE G. BRADLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,064,905 Green Dec. 22, 1936 2,093,847 Pruden Sept. 21, 1937 2,137,023 Monk Nov. 15, 1938 2,164,960 Stockton et al.- July 4, 1939 2,176,868 Boswau Oct. 24, 1939 2,265,056 Bowers Dec. 2, 1941 2,399,738 Howe May 7, 1946 2,419,593 Robinson Apr. 29, 1947 FOREIGN PATENTS Number Country Date 311,450 Great Britain May 13, 1929

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