CA1312395C - Network interface and communications terminal - Google Patents
Network interface and communications terminalInfo
- Publication number
- CA1312395C CA1312395C CA000609405A CA609405A CA1312395C CA 1312395 C CA1312395 C CA 1312395C CA 000609405 A CA000609405 A CA 000609405A CA 609405 A CA609405 A CA 609405A CA 1312395 C CA1312395 C CA 1312395C
- Authority
- CA
- Canada
- Prior art keywords
- bit rate
- type
- encryption
- network interface
- digital
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/05—Electric or magnetic storage of signals before transmitting or retransmitting for changing the transmission rate
Abstract
Abstract Network Interface and Communications Terminal According to the invention, for connections between terminals connected to different networks, the ter-minals intended for connection to the network having the higher capacity are so equipped that, alternatively (I, II), they could also operate at the network having the lower capacity. In these terminals as well as at the inter-face between the two networks, simple network interface de-vices (30, 60) are inserted which insert and extract the filler bits in a suitable manner.
Description
:~3~`3~
P 38 31 215.8 Network Interface and Communicat;ons Terminal The present invention relates to a network interface for use between two digital telecommunication networks with transmission channels of different capacity and, thus, different bit rate, particularly 64-kb/s and 16-kb/s telecommunication networks, and to communica-tions terminals, particularly telephone terminals, which are designed for connection to that of the two telecommunication networks having the transmission channels of higher capacity.
To meet different requirements, telecommunication net-works with different types of modulation and different transmission rates are used.
For stationary telecommunication networks, such as those of postal administrations,the CCITT recommendations are generally applied~ i.e., in Europe, a channel bit rate of 64 kbls and pulse-code modulation with A-law companding.
For economic reasons, stationary telecommunication net-works of other administrations are also implemented in ZPL-Bs/Ke/Lo 27 July, 1989 W. Dietze 14 ~3~ 23~5 accordance with those CCITT recommendations~ This applies in particular with reaard to the introduction of ISDN
for subscribers in such telecommunication networks.
Besides the stationary telecommunication networks, however, there are also tactical telecommunicat;on networks. The latter are characterized by great mobility of the subscribers and possible strong interference on the transmission links~ Therefore, a channel bit rate of 16 kb/s or 32 kb/s and other modulation types, e.g., delta modulation in different variants, have been established for tactical telecommunication networks.
The same applies analogously to the new civil mobile radio network (C-net), which is currently being intro-duced.
The different channel bit rates and types of modulation cause problems during connections between subscriber facilities of different telecommunication networks, particularly if the speech or data is to be trans-mitted in èncrypted form. In either case, it is not possible to simply convert the signals from one channel bit rate and type of modulation to another and back.
In general, encryption and decryption in a connection between two telecommunication networks can be accomplished by performing a single-channel encryp-tion ;n each of the two telecommunication networks and a code conversion (transcoding) at the interface between the different telecommunication networks.
;:
W. ~ietze 14 ':
13~3~
One of the disadvantages of this solution is that it does not permit end-to-end encryption, since at the interface between the two different telecommunication networks, the information must be present in plain text so that a code conversion can be performed.
IF the code conversion takes place at the exchange, stringent requirements must be placed on crosstaLk attenuation between the individual connect;ons wh;ch can be met onLy with great difficulty, if at all. These requirements are reduced if the code conversion is performed in a special facility.
It is the object of the invention to provide a network interface and an application thereof which prov;des a connection between two networks that poses no problems.
This object is attained by a network interface accord-ing to the teaching of claim 1 and by a communications terminal according to the teach;ng of claim 3. Further advantageous aspects of the invention are claimed in the subclaims.
,:
According to the invention, for connections between terminals connected to different networks, the ter-minals intended for connection to the network having the higher capacity are so equipped that, alternatively~
they could also operate at the network having the lower capacity. In these terminals as well as at the inter-face between the two networks, simple network interface W. Dietze 14 - 4 - 13~23~
devices are i,nserted which insert and extract the filler bits in a suitable manner.
Unlike the aforementioned variants, the proposed solution permits both end-to-end encryption and data transmission, with no particularly stringent requirements being placed on - crosstalk attenuation and only two single-channel encryption and decryption devices having to be used in a connection.
The proposed solution eliminates the need to transcode the modulation types; instead, telecommunication network A
must include an encoding facility both for modulation type A, e.g., PCM, and for modulation type B, e.g., delta modulation.
Single-channel encryption and decryption devices can be inserted both into a 16-kb/s connection and into a 64-kb/s connection, as will be shown later.
According to a broad aspect of the invention there is provided a terminal, for encrypted digital communication, the terminal comprising: an encryption device; a decryption device;
a network interface for changing an incoming digital transmission from a first bit rate to a second bit rate lower than said first bit rate and for changing an outgoing digital transmission from said second bit rate to said first bit rate; first means for directly connecting the encryption and decryption devices to a digital communication channel having a predetermined first capacity and a bit rate equal to said first bit rate and for operating said encryption and decryption devices at said first bit rate; second means for indirectly connecting said devices to said digital communication channel via said network interface so ,~
13 1 ~
as to produce a terminal output that is also compatible with a second capacity and bit rate less than the first capacity and bit rate and for operating said encryption and decryption devices at said second bit rate; and switch means for alternat-ing control between said first means and said second means.
According to another broad aspect of the invention there is provided a telephone terminal for encrypted voice communication, the terminal comprising: an encoder of a first type; an encryption device; a decoder of the first type; a decryption device; first means for connecting the encoder of the first type via the encryption device and for connecting the decoder of the first type via the decryption device to a digital telecommunication channel having a predetermined first capacity and bit rate, wherein the encoder and decoder of the first type convert analog signals to digital signals and back at the first bit rate, with the encryption and decryption devices operating at a first clock rate corresponding to the bit rate in a first telecommunication network; an encoder of a second type; a decoder of a second type; a network interface having an incoming portion for changing an incoming digital transmission from said first bit rate to a second bit rate lower than said first bit rate and an output portion for changing an outgoing digital transmission from said second bit rate to said first bit rate;
second means for connecting the encoder of the second type via the encryption device and via the output portion of the network interface and for connecting the decoder of the second type via the decryption device and via the input portion of the network ;"~", - 4b - 13~3~
620~6-215 interface to said digital telecommunication channe] having said predetermined first capacity and bit rate, wherein the encoder and decoder of the second type convert analog signals to digital signals and back at a second bit rate less than the first capacity and bit rate, with the encryption and decryption devices operating at a second clock rate corresponding to the second bit rate; and means for switching the encryption and decryption devices between said first and second clock rates.
The invention will now be explained in more detail with reference to an embodiment thereof shown in the accompany-ing drawing.
The drawing shows a telephone terminal with devices for pulse-code modulation at 64-kb/s, devices for delta modulation at 16-kb/s, encryption and decryption devices, a network interface, and changeover facilities.
For connection to the 64-kb/s telecommunication network, the telephone terminal has, on the send side r a micro-phone 11 (M), a PCM encoder 12, and an encryption device 13 (ZS)' which are connected to the line 14, and, ~3~23~
on the receive side, a receiver 41 (H), a PCM decoder 42, and a decryption device 43, which are connected to the line 44. The PCM encoder 12 and the PCM decoder 42 convert analog signals to digital signals and back and perform the necessary companding. The digital de-vices operate at a 64-kHz clock rate.
The transmission equipment via which the lines 14 and 44 are connected to the central-office trunks, e.g., line coder, power feeding equipment, and 2- to 4-wire converter, is not shown.
For connection to a 16-kb/s telecommunication network, the telephone terminal additionally includes, on the send side, a 16-kHz delta encoder 21~and a changeover device 22 for clocking the encryption device 13 at 16 kHz instead of 64 kHz and, on the receive side, a 16-kHz delta decoder 51 and a changeover device 52 for clocking the decryption device 43 at 16 kHz instead of 64 kHz~
! The telephone terminal further includes a network inter-face consisting of a send-side portion 30 and a receive-side portion 60. This network interface makes it possible to operate the telephone terminal as a 16-kb/s terminal in connection with another 16-kb/s terminal although there is only a connection to the 16-kb/s net-work.
: ~
Via switches S1 to S6, the terminal is switched between the two modes. In the figure, all switches are shown W~ Dietze 14 .
~3~239~
in pos;tion I, which permits a connection with a remote 16 kb/s station. In position II (not shown),a connec-tion with a remote 64-kbts station is possible.
The send-side portion 30 of the network interface accepts the incoming useful bits at a 16-kHz clock rate and passes them on at a 64-kHz clock rate. The filler bits must be insertedin between. In the above numerical example, three filler bits are required for each useful bit. The spacing of the useful bits remains unchanged, however.
In the simplest case, the filler bits have the same value as the respective useful bitspreceding them.
Th;s can be implemented, for example, by writing in-to a buffer at a 16-kHz clock rate and reading there-from at a 64-kHz clock rate, with each bit being read four times in succession. The two clock signals need not be in synchronism.
- . .
Another possibility is to use 4-bit parallel-to-serial converters, which are preferably implemented with shift registers. Each incoming useful bit is supplied to all four inputs in parallel and is thus output - four times in succession. It is also possible to feed the useful bits only to the first and third inputs and to either connect the two other inputs to a fixed potential or 3pply the useful bits to them in inverted formu In this manner, as frequent a change of state as , W. Dietze 14 ~ .
.~31~3~
possible is achieved, which is often desirable. The use-ful bits, i.e., the respect;ve first bits of the four-bit groups, can still be unambiguously evaluated.
The receive-side portion oO of the network interface ope-rates conversely. Every fourth bit is extracted from the in-coming 64-kb/s data stream and is passed on in a 16-kb/s data stream. If the filler bits have the same value asthe respective preceding ùseful bits, it is not even necessary to see to it that the first bit of each four bit-group is passed on.
This can again be implemented with a buffer from which only one of every four successively written bits is read, or with a 4-bit serial-to-parallel conuerter having only one of its four outputs wired.
While the realization using parallel-to-serlal and serial-to-parallel converters is suitable only if the higher transmission rate is an integral multiple of the lower transmission rate, the realization using buffers into which data is written at one clock rate andfrom which data is read at another clock rate is applicable to arbitrary ratios of the transmission rates.
From the foregoing it follows that switching of the telephone terminals from one mode to the other is necessary only in the telecommunication network with the high transmission rate. The switching can be W. Dietze 14 ~3~3~
effected manually by the subscriber or automat;cally.
Automatic switchover can be effected by arrang-ing that the equipment of the exchange of the a-subscriber in the 64-kb/s telecommunication net~
word recognizes from the dialled des~ination address whether a changeover is necessary, and, if so, initiates a corresponding instruction to the dev;ces i.n the terminal of the a-subscri.ber.
Switchover can also be effected by sending a back-ward signal from the equipment in the network of of the called subscriber to the devices in the term;nal of the calling subscr;ber after establish-ment of a connection, thus causing a changeover.
When a connection is established from the b-sub-scriber in the 16-kbts telecommunication net-word to the a-subscriber, a forward si.gnal i.s sent from the equipment in the network of the b-subscriber to the terminal of the a-subscriber, thus causing a changeover.
:
The equipment of the exchange of the a-subscriber recogni.zes from the source address whether change-over is necessary, and, if so, initiates a corresponding i.nstruction to the terminal of the a-sub,criber.
.
W. Dietz.e 14 .
~L3~3~
9 _ - The switching signal can also be used to switch the power supplies of the individual pieces of equipment so as to reduce power consumption, for example.
The signalling required to switch between the two modes can be in-band signalling, since it takes place in the connection setup phase, but it can also be accomplished over a separate service channel tD channel ;n ISDN).
W. Dietze 14 '
P 38 31 215.8 Network Interface and Communicat;ons Terminal The present invention relates to a network interface for use between two digital telecommunication networks with transmission channels of different capacity and, thus, different bit rate, particularly 64-kb/s and 16-kb/s telecommunication networks, and to communica-tions terminals, particularly telephone terminals, which are designed for connection to that of the two telecommunication networks having the transmission channels of higher capacity.
To meet different requirements, telecommunication net-works with different types of modulation and different transmission rates are used.
For stationary telecommunication networks, such as those of postal administrations,the CCITT recommendations are generally applied~ i.e., in Europe, a channel bit rate of 64 kbls and pulse-code modulation with A-law companding.
For economic reasons, stationary telecommunication net-works of other administrations are also implemented in ZPL-Bs/Ke/Lo 27 July, 1989 W. Dietze 14 ~3~ 23~5 accordance with those CCITT recommendations~ This applies in particular with reaard to the introduction of ISDN
for subscribers in such telecommunication networks.
Besides the stationary telecommunication networks, however, there are also tactical telecommunicat;on networks. The latter are characterized by great mobility of the subscribers and possible strong interference on the transmission links~ Therefore, a channel bit rate of 16 kb/s or 32 kb/s and other modulation types, e.g., delta modulation in different variants, have been established for tactical telecommunication networks.
The same applies analogously to the new civil mobile radio network (C-net), which is currently being intro-duced.
The different channel bit rates and types of modulation cause problems during connections between subscriber facilities of different telecommunication networks, particularly if the speech or data is to be trans-mitted in èncrypted form. In either case, it is not possible to simply convert the signals from one channel bit rate and type of modulation to another and back.
In general, encryption and decryption in a connection between two telecommunication networks can be accomplished by performing a single-channel encryp-tion ;n each of the two telecommunication networks and a code conversion (transcoding) at the interface between the different telecommunication networks.
;:
W. ~ietze 14 ':
13~3~
One of the disadvantages of this solution is that it does not permit end-to-end encryption, since at the interface between the two different telecommunication networks, the information must be present in plain text so that a code conversion can be performed.
IF the code conversion takes place at the exchange, stringent requirements must be placed on crosstaLk attenuation between the individual connect;ons wh;ch can be met onLy with great difficulty, if at all. These requirements are reduced if the code conversion is performed in a special facility.
It is the object of the invention to provide a network interface and an application thereof which prov;des a connection between two networks that poses no problems.
This object is attained by a network interface accord-ing to the teaching of claim 1 and by a communications terminal according to the teach;ng of claim 3. Further advantageous aspects of the invention are claimed in the subclaims.
,:
According to the invention, for connections between terminals connected to different networks, the ter-minals intended for connection to the network having the higher capacity are so equipped that, alternatively~
they could also operate at the network having the lower capacity. In these terminals as well as at the inter-face between the two networks, simple network interface W. Dietze 14 - 4 - 13~23~
devices are i,nserted which insert and extract the filler bits in a suitable manner.
Unlike the aforementioned variants, the proposed solution permits both end-to-end encryption and data transmission, with no particularly stringent requirements being placed on - crosstalk attenuation and only two single-channel encryption and decryption devices having to be used in a connection.
The proposed solution eliminates the need to transcode the modulation types; instead, telecommunication network A
must include an encoding facility both for modulation type A, e.g., PCM, and for modulation type B, e.g., delta modulation.
Single-channel encryption and decryption devices can be inserted both into a 16-kb/s connection and into a 64-kb/s connection, as will be shown later.
According to a broad aspect of the invention there is provided a terminal, for encrypted digital communication, the terminal comprising: an encryption device; a decryption device;
a network interface for changing an incoming digital transmission from a first bit rate to a second bit rate lower than said first bit rate and for changing an outgoing digital transmission from said second bit rate to said first bit rate; first means for directly connecting the encryption and decryption devices to a digital communication channel having a predetermined first capacity and a bit rate equal to said first bit rate and for operating said encryption and decryption devices at said first bit rate; second means for indirectly connecting said devices to said digital communication channel via said network interface so ,~
13 1 ~
as to produce a terminal output that is also compatible with a second capacity and bit rate less than the first capacity and bit rate and for operating said encryption and decryption devices at said second bit rate; and switch means for alternat-ing control between said first means and said second means.
According to another broad aspect of the invention there is provided a telephone terminal for encrypted voice communication, the terminal comprising: an encoder of a first type; an encryption device; a decoder of the first type; a decryption device; first means for connecting the encoder of the first type via the encryption device and for connecting the decoder of the first type via the decryption device to a digital telecommunication channel having a predetermined first capacity and bit rate, wherein the encoder and decoder of the first type convert analog signals to digital signals and back at the first bit rate, with the encryption and decryption devices operating at a first clock rate corresponding to the bit rate in a first telecommunication network; an encoder of a second type; a decoder of a second type; a network interface having an incoming portion for changing an incoming digital transmission from said first bit rate to a second bit rate lower than said first bit rate and an output portion for changing an outgoing digital transmission from said second bit rate to said first bit rate;
second means for connecting the encoder of the second type via the encryption device and via the output portion of the network interface and for connecting the decoder of the second type via the decryption device and via the input portion of the network ;"~", - 4b - 13~3~
620~6-215 interface to said digital telecommunication channe] having said predetermined first capacity and bit rate, wherein the encoder and decoder of the second type convert analog signals to digital signals and back at a second bit rate less than the first capacity and bit rate, with the encryption and decryption devices operating at a second clock rate corresponding to the second bit rate; and means for switching the encryption and decryption devices between said first and second clock rates.
The invention will now be explained in more detail with reference to an embodiment thereof shown in the accompany-ing drawing.
The drawing shows a telephone terminal with devices for pulse-code modulation at 64-kb/s, devices for delta modulation at 16-kb/s, encryption and decryption devices, a network interface, and changeover facilities.
For connection to the 64-kb/s telecommunication network, the telephone terminal has, on the send side r a micro-phone 11 (M), a PCM encoder 12, and an encryption device 13 (ZS)' which are connected to the line 14, and, ~3~23~
on the receive side, a receiver 41 (H), a PCM decoder 42, and a decryption device 43, which are connected to the line 44. The PCM encoder 12 and the PCM decoder 42 convert analog signals to digital signals and back and perform the necessary companding. The digital de-vices operate at a 64-kHz clock rate.
The transmission equipment via which the lines 14 and 44 are connected to the central-office trunks, e.g., line coder, power feeding equipment, and 2- to 4-wire converter, is not shown.
For connection to a 16-kb/s telecommunication network, the telephone terminal additionally includes, on the send side, a 16-kHz delta encoder 21~and a changeover device 22 for clocking the encryption device 13 at 16 kHz instead of 64 kHz and, on the receive side, a 16-kHz delta decoder 51 and a changeover device 52 for clocking the decryption device 43 at 16 kHz instead of 64 kHz~
! The telephone terminal further includes a network inter-face consisting of a send-side portion 30 and a receive-side portion 60. This network interface makes it possible to operate the telephone terminal as a 16-kb/s terminal in connection with another 16-kb/s terminal although there is only a connection to the 16-kb/s net-work.
: ~
Via switches S1 to S6, the terminal is switched between the two modes. In the figure, all switches are shown W~ Dietze 14 .
~3~239~
in pos;tion I, which permits a connection with a remote 16 kb/s station. In position II (not shown),a connec-tion with a remote 64-kbts station is possible.
The send-side portion 30 of the network interface accepts the incoming useful bits at a 16-kHz clock rate and passes them on at a 64-kHz clock rate. The filler bits must be insertedin between. In the above numerical example, three filler bits are required for each useful bit. The spacing of the useful bits remains unchanged, however.
In the simplest case, the filler bits have the same value as the respective useful bitspreceding them.
Th;s can be implemented, for example, by writing in-to a buffer at a 16-kHz clock rate and reading there-from at a 64-kHz clock rate, with each bit being read four times in succession. The two clock signals need not be in synchronism.
- . .
Another possibility is to use 4-bit parallel-to-serial converters, which are preferably implemented with shift registers. Each incoming useful bit is supplied to all four inputs in parallel and is thus output - four times in succession. It is also possible to feed the useful bits only to the first and third inputs and to either connect the two other inputs to a fixed potential or 3pply the useful bits to them in inverted formu In this manner, as frequent a change of state as , W. Dietze 14 ~ .
.~31~3~
possible is achieved, which is often desirable. The use-ful bits, i.e., the respect;ve first bits of the four-bit groups, can still be unambiguously evaluated.
The receive-side portion oO of the network interface ope-rates conversely. Every fourth bit is extracted from the in-coming 64-kb/s data stream and is passed on in a 16-kb/s data stream. If the filler bits have the same value asthe respective preceding ùseful bits, it is not even necessary to see to it that the first bit of each four bit-group is passed on.
This can again be implemented with a buffer from which only one of every four successively written bits is read, or with a 4-bit serial-to-parallel conuerter having only one of its four outputs wired.
While the realization using parallel-to-serlal and serial-to-parallel converters is suitable only if the higher transmission rate is an integral multiple of the lower transmission rate, the realization using buffers into which data is written at one clock rate andfrom which data is read at another clock rate is applicable to arbitrary ratios of the transmission rates.
From the foregoing it follows that switching of the telephone terminals from one mode to the other is necessary only in the telecommunication network with the high transmission rate. The switching can be W. Dietze 14 ~3~3~
effected manually by the subscriber or automat;cally.
Automatic switchover can be effected by arrang-ing that the equipment of the exchange of the a-subscriber in the 64-kb/s telecommunication net~
word recognizes from the dialled des~ination address whether a changeover is necessary, and, if so, initiates a corresponding instruction to the dev;ces i.n the terminal of the a-subscri.ber.
Switchover can also be effected by sending a back-ward signal from the equipment in the network of of the called subscriber to the devices in the term;nal of the calling subscr;ber after establish-ment of a connection, thus causing a changeover.
When a connection is established from the b-sub-scriber in the 16-kbts telecommunication net-word to the a-subscriber, a forward si.gnal i.s sent from the equipment in the network of the b-subscriber to the terminal of the a-subscriber, thus causing a changeover.
:
The equipment of the exchange of the a-subscriber recogni.zes from the source address whether change-over is necessary, and, if so, initiates a corresponding i.nstruction to the terminal of the a-sub,criber.
.
W. Dietz.e 14 .
~L3~3~
9 _ - The switching signal can also be used to switch the power supplies of the individual pieces of equipment so as to reduce power consumption, for example.
The signalling required to switch between the two modes can be in-band signalling, since it takes place in the connection setup phase, but it can also be accomplished over a separate service channel tD channel ;n ISDN).
W. Dietze 14 '
Claims (3)
1. A terminal, for encrypted digital communication, the terminal comprising:
an encryption device;
a decryption device;
a network interface for changing an incoming digital transmission from a first bit rate to a second bit rate lower than said first bit rate and for changing an outgoing digital transmission from said second bit rate to said first bit rate;
first means for directly connecting the encryption and decryption devices to a digital communication channel having a predetermined first capacity and a bit rate equal to said first bit rate and for operating said encryption and decryption devices at said first bit rate;
second means for indirectly connecting said devices to said digital communication channel via said network interface so as to produce a terminal output that is also compatible with a second capacity and bit rate less than the first capacity and bit rate and for operating said encryption and decryption devices at said second bit rate; and switch means for alternating control between said first means and said second means.
an encryption device;
a decryption device;
a network interface for changing an incoming digital transmission from a first bit rate to a second bit rate lower than said first bit rate and for changing an outgoing digital transmission from said second bit rate to said first bit rate;
first means for directly connecting the encryption and decryption devices to a digital communication channel having a predetermined first capacity and a bit rate equal to said first bit rate and for operating said encryption and decryption devices at said first bit rate;
second means for indirectly connecting said devices to said digital communication channel via said network interface so as to produce a terminal output that is also compatible with a second capacity and bit rate less than the first capacity and bit rate and for operating said encryption and decryption devices at said second bit rate; and switch means for alternating control between said first means and said second means.
2. A telephone terminal for encrypted voice communication, the terminal comprising:
an encoder of a first type;
an encryption device;
a decoder of the first type;
a decryption device;
first means for connecting the encoder of the first type via the encryption device and for connecting the decoder of the first type via the description device to a digital tele-communication channel having a predetermined first capacity and bit rate, wherein the encoder and decoder of the first type convert analog signals to digital signals and back at the first bit rate, with the encryption and decryption devices operating at a first clock rate corresponding to the bit rate in a first telecommunication network;
an encoder of a second type;
a decoder of a second type;
a network interface having an incoming portion for changing an incoming digital transmission from said first bit rate to a second bit rate lower than said first bit rate and an output portion for changing an outgoing digital transmission from said second bit rate to said first bit rate;
second means for connecting the encoder of the second type via the encryption device and via the output portion of the network interface and for connecting the decoder of the second type via the decryption device and via the input portion of the network interface to said digital telecommunication channel having said predetermined first capacity and bit rate, wherein the encoder and decoder of the second type convert analog signals to digital signals and back at a second bit rate less than the first capacity and bit rate, with the encryption and decryption devices operating at a second clock rate corres-ponding to the second bit rate; and means for switching the encryption and decryption devices between said first and second clock rates.
an encoder of a first type;
an encryption device;
a decoder of the first type;
a decryption device;
first means for connecting the encoder of the first type via the encryption device and for connecting the decoder of the first type via the description device to a digital tele-communication channel having a predetermined first capacity and bit rate, wherein the encoder and decoder of the first type convert analog signals to digital signals and back at the first bit rate, with the encryption and decryption devices operating at a first clock rate corresponding to the bit rate in a first telecommunication network;
an encoder of a second type;
a decoder of a second type;
a network interface having an incoming portion for changing an incoming digital transmission from said first bit rate to a second bit rate lower than said first bit rate and an output portion for changing an outgoing digital transmission from said second bit rate to said first bit rate;
second means for connecting the encoder of the second type via the encryption device and via the output portion of the network interface and for connecting the decoder of the second type via the decryption device and via the input portion of the network interface to said digital telecommunication channel having said predetermined first capacity and bit rate, wherein the encoder and decoder of the second type convert analog signals to digital signals and back at a second bit rate less than the first capacity and bit rate, with the encryption and decryption devices operating at a second clock rate corres-ponding to the second bit rate; and means for switching the encryption and decryption devices between said first and second clock rates.
3. The telephone terminal of claim 2, wherein said first type is pulse-code-modulation, and said second type is delta modulation.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3831215.8 | 1988-09-14 | ||
| DE3831215A DE3831215A1 (en) | 1988-09-14 | 1988-09-14 | NETWORK TRANSFER DEVICE AND TELECOMMUNICATION DEVICE |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1312395C true CA1312395C (en) | 1993-01-05 |
Family
ID=6362919
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000609405A Expired - Fee Related CA1312395C (en) | 1988-09-14 | 1989-08-25 | Network interface and communications terminal |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US5058156A (en) |
| EP (1) | EP0359156A3 (en) |
| CA (1) | CA1312395C (en) |
| DE (1) | DE3831215A1 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3915043A1 (en) * | 1989-05-08 | 1990-11-15 | Siemens Ag | MESSAGE TRANSFER SYSTEM |
| US5247626A (en) * | 1990-05-29 | 1993-09-21 | Advanced Micro Devices, Inc. | Fddi controller having flexible buffer management |
| DE69132460T2 (en) * | 1990-11-29 | 2001-03-15 | Fujitsu Ltd | ISDN interface circuit |
| DE59208645D1 (en) * | 1991-05-13 | 1997-07-31 | Siemens Schweiz Ag | Arrangement with at least one computer that can be connected to a telecommunications network, and an application of this arrangement |
| GB2273022B (en) * | 1992-11-25 | 1996-05-22 | Sony Broadcast & Communication | Processing sampled data |
| US5917827A (en) * | 1996-05-15 | 1999-06-29 | Alcatel Usa Sourcing, L.P. | Multiple rate network interface and method |
| WO2003096612A1 (en) * | 2002-05-09 | 2003-11-20 | Niigata Seimitsu Co., Ltd. | Encryption device, encryption method, and encryption system |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2267669B1 (en) * | 1974-04-12 | 1977-03-04 | Ibm France | |
| US4087626A (en) * | 1976-08-04 | 1978-05-02 | Rca Corporation | Scrambler and unscrambler for serial data |
| JPS55147060A (en) * | 1979-05-02 | 1980-11-15 | Nec Corp | Fsk and psk modulating circuit |
| JPS5691548A (en) * | 1979-12-25 | 1981-07-24 | Nec Corp | Link speed matching system |
| US4330689A (en) * | 1980-01-28 | 1982-05-18 | The United States Of America As Represented By The Secretary Of The Navy | Multirate digital voice communication processor |
| DE3033871C2 (en) * | 1980-09-09 | 1982-11-25 | Siemens AG, 1000 Berlin und 8000 München | Messaging system |
| US4484327A (en) * | 1983-05-02 | 1984-11-20 | The United States Of America As Represented By The Secretary Of The Army | Pulse code modulation rate converter |
| US4538286A (en) * | 1983-07-26 | 1985-08-27 | Gte Communications Products Corporation | Data rate conversion and supervisory bit insertion in a data system |
| JPH0632522B2 (en) * | 1983-12-29 | 1994-04-27 | 富士通株式会社 | Digital signal transmission method |
| DE3411881A1 (en) * | 1984-03-30 | 1985-10-10 | Siemens AG, 1000 Berlin und 8000 München | METHOD AND CIRCUIT ARRANGEMENT FOR TRANSMITTING DATA SIGNAL BITS APPLYING WITH A FIRST BITRATE IN A BIT CURRENT WITH A SECOND BITRATE HIGHER THAN THE FIRST BITRATE |
| US4716561A (en) * | 1985-08-26 | 1987-12-29 | American Telephone And Telegraph Company, At&T Bell Laboratories | Digital transmission including add/drop module |
-
1988
- 1988-09-14 DE DE3831215A patent/DE3831215A1/en not_active Withdrawn
-
1989
- 1989-08-25 CA CA000609405A patent/CA1312395C/en not_active Expired - Fee Related
- 1989-09-09 EP EP19890116704 patent/EP0359156A3/en not_active Ceased
- 1989-09-11 US US07/405,345 patent/US5058156A/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| EP0359156A3 (en) | 1992-01-02 |
| US5058156A (en) | 1991-10-15 |
| DE3831215A1 (en) | 1990-03-22 |
| EP0359156A2 (en) | 1990-03-21 |
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| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |