WO1999007134A1

WO1999007134A1 - Hand free system

Info

Publication number: WO1999007134A1
Application number: PCT/DE1998/001041
Authority: WO
Inventors: Rolf Oberstelehn
Original assignee: Siemens Aktiengesellschaft
Priority date: 1997-07-28
Filing date: 1998-04-09
Publication date: 1999-02-11
Also published as: EP1000501A1

Abstract

The invention concerns a method for regulating a hand free system deviation comprising a transmitted signal branch (MK, MV) and a received signal branch (WV, LP), each including adjustable attenuation stages (SD, ED). The method is characterised in that it consists in determining a value for the branch point coupling (GK), and in adjusting a deviation value for controlling the attenuation stages (SD, ED).

Description

description

Speakerphone

The invention relates to a method according to the preamble of patent claim 1.

A hands-free device known per se is shown in FIG. It has a transmission signal branch via which the signals picked up by a microphone MK are sent via a microphone amplifier MV and a transmission attenuation stage SD to an electronic fork EG, for example. The electronic fork EG is preferably connected to an analog subscriber line, a so-called a / b line. The hands-free device also has a reception signal branch, via which the signals applied to the electronic fork EG are sent to a loudspeaker LP via an amplifier V, a reception attenuation stage ED and a playback amplifier WV. The transmission and reception damping stages are controlled by a stroke control HS. For this purpose, the stroke control HS is connected, for example, via a logarithmic amplifier LV 1 to the output-side connection of the transmission attenuation stage SD, and via a logarithmic amplifier LV2 to the input-side connection of the reception attenuation stage ED.

The hands-free device is installed, for example, in a communication terminal. There is an acoustic coupling AK between the loudspeaker LP and the microphone MK due to the local proximity of the two components, for example in a telephone. Between the transmit signal branch and the receive signal branch there is a fork coupling GK acting via the electronic fork EG.

In order to ensure that the hands-free system functions properly, no feedback phenomena may occur between the transmit signal and receive signal branches. that is, the speakerphone must not whistle. This is achieved by a circular gain with a value of less than 0 dB in the hands-free system. For this purpose, either the transmission damping stage SD in the transmission signal branch or the reception damping stage ED in the reception signal branch is damped by the set stroke via the stroke control HS. The stroke control HS is connected on the input side via two or more logarithmic amplifiers LV1, LV2 to the transmit signal and receive signal branches. In the stroke control HS, a decision is made as to which of the speech directions, transmit signal or receive signal branches are damped or undamped around the stroke.

In the case of acoustically well-adapted devices, this stroke is around 30 to 40 dB. The higher the stroke has to be selected, the more difficult it is to switch in the other direction while the interlocutor is still speaking. In addition, with high strokes, the impression of a dead line can arise.

With today's analog hands-free speakers, the stroke must now be measured on an open line. The hands-free system must not show a whistle when the line is open, i.e. not closed. However, this state of the open line is not a state of conversation. In the call state, the set stroke could be reduced by approx. 6 to 10 dB in order to significantly improve the intercom behavior. The known analog hands-free devices are tuned via setting resistors so that there is no whistling tendency when the line is open. This means that the hands-free speakers are not optimally adjusted and cannot be optimized during operation.

The invention is based on the object of specifying a method for stroke control of a hands-free device which enables a reduced stroke in the conversation state. This object is achieved by the entitlement l specified in the patent applica ^¬ characteristics.

The method according to the invention ultimately detects an open or a closed subscriber line. The hands-free control stroke is set accordingly. In an embodiment of the invention, an optimization of the listening back in connection with a multi-stage adjustment of the control stroke is possible. This leads to a further improvement in the two-way communication.

The components necessary for the method according to the invention have already been incorporated into new speech circuit concepts, but for other purposes. As a result, the invention can be implemented in a practically cost-neutral manner.

The invention is described below with reference to an embodiment shown in the drawing. Show

1 shows a known hands-free device, and

2 shows a supplemented hands-free device which is suitable for carrying out the method according to the invention.

The modules required for this are a microprocessor P, an output module AB and an analog-digital converter AD. The output module AB is connected to the processor P, for example, via a bus, which is not described in more detail. The processor P is also connected to the stroke control HS and via a serial bus SB to the analog digital converter AD.

In the method according to the invention, the processor P feeds signals into the transmission signal branch via the output module AB. For this purpose, the output module AB is connected, for example, to the output end of the transmission attenuation stage SD. The signals can contain one or more tones. These signals reach the receiver via the fork coupling GK. catch signal branch. The level of these signals fed into the transmission signal branch is measured in the reception signal branch. For this purpose, for example, the analog digital converter AD is connected to the input-side connection of the reception attenuation stage ED. The value of the level is calculated in the processor P, and a stroke value for the control of the hands-free device is set in the stroke control HS in accordance with this value.

The level value measured in the received signal branch can be used to determine whether the hands-free device is located on an open connecting line a / b or not. If the speakerphone or the communication terminal containing it is not on an open line, the hub is set to the preset hub values for hands-free operation.

If the line is open or poorly terminated, the stroke remains correspondingly large. This ensures that there is no whistling. This setting should be selected, for example, when dialing with the handset on-hook.

The signals or tones fed into the transmission signal branch should preferably be counted in such a way that there is no conflict with DTMF frequencies or interference is prevented as far as possible. It may also be necessary to differentiate between an outgoing and an incoming call in order to avoid calibration during an incoming call.

The communication terminal can thus be set to strokes in the range of 20 to 34 dB, for example, which leads to a corresponding improvement in the intercom behavior. In addition, it would not whistle even if the line was not or poorly terminated. There would also be no whistling during calibration, since it is preferable to start with a high stroke.

In a further development of the method according to the invention, it would be possible for the customer's response behavior to be measured automatically in several stages, since the response behavior can be influenced to a certain extent by the processor, and a customer-optimized adaptation can thus be brought about. This customer-optimized adaptation allows even lower strokes during normal operation of the hands-free system. It may be necessary to adjust the setting of the logarithmic amplifiers LV1 and LV2 to the changed stroke control, since the factory setting is usually only optimized for one stroke.

In a further embodiment of the invention, a connection-specific adaptation is also possible using the call number display (CLIP function) announced by Deutsche Telekom, in that the necessary parameters are automatically saved for each subscriber. When the corresponding subscriber calls, these parameters can be called up and the hands-free system set accordingly.

Claims

claims

1. Method for stroke control of a hands-free device with a transmission signal (MK, MV) and a reception signal branch (WV LP), each with adjustable damping stages (SD, ED), the transmission signal (MK, MV) and the reception signal branch (WV LP) are connected to a particularly electronic fork (EG), characterized in that a value for the fork coupling (GK) is determined and a corresponding stroke value is set for controlling the damping stages (SD, ED).

2. The method according to claim 1, characterized in that for determining the fork coupling (GK) signals are fed into the transmission signal branch (MK, MV), and the associated level value is determined in the reception signal branch (WV LP).

3. The method according to claim 1 or 2, characterized in that the stroke value is adapted in several stages to different values of the fork coupling (GK) due to different line conditions.

4. The method according to claim 3, characterized in that the stroke value determined for a subscriber together with the

The subscriber's number is saved.