FR2517911A1 - CONTROL CIRCUIT FOR HANDS-FREE TELEPHONE CONVERSATION DEVICE - Google Patents

Abstract

THREE OPERATING STATES - TRANSMIT, IDLE, RECEPTION - ARE DETERMINED BY CONSTANT INCREASES OR DECREASES IN THE TELEPHONE VOLTAGE LEVEL, PRODUCED BY TWO SWITCHING AMPLIFIERS SV1, SV2 AND TWO WEAKNESSES DG1, DG2 OF THE AMLIFICATIONS AND COMMANDS RV1, RV2, RV3 AND LEVEL DETECTORS PD1, PD2, PD3.

Description

Control circuit for hands-on telephone conversation device

  The present invention relates to a control circuit for a hands-free conversation device in telephone systems, comprising a 4-wire 2-wire terminator circuit, a voice-controlled voice identification and

  switching device for the transmitter amplifiers

  transmitters and receivers, including the ordering criteria for

  switching on and off of weakening organs

  are derived from the voltage levels

  sound. A hands-free conversation system must

  telephone without using the telephone handset.

  For this purpose, the listening circuit of the telephone

  is replaced by a receiver amplifier and a

  loudspeaker, while the speech circuit is replacing

  by a transmitter amplifier and a microphone.

  of the four-wire transmission in the transmitting

  the two-wire transmission of the connection lines is carried out in a terminating circuit.

  two signal paths are decoupled by the weakening

  Terminator loss The loss of the terminator depends on

  adaptation of a balancer to the connection line

  and thus of each telephone link.

  The need not to exceed a specific value

  of the reference emission attenuation, for example + 12 d B, and to obtain as loud a sound intensity as possible in the receiving direction, may cause reaction whistling due to the amplifications which, in the same way cases are necessary for this purpose in the

  transmitter channel and receiver channel as an increase

  loss of the terminator by adaptation of the

  balancers with line impedance depending on the link

  sound is very difficult to achieve, we use

  voice control systems that "open" or "close" the transmitter and receiver channels in the opposite direction

  hands-free conversation device -

  In the event of the opening and closing of the signal paths of the hands-free conversation device, the handset's duplex communication capability is lost and the result is a simplex communication-this is very poorly felt, especially

  by the subscriber who does not speak hands free He has the

  pressure to speak in a dead line Conversely, the subscriber does not speak hands free, hears, when the transmitter channel and the receiver channel are fully open at the same time, the echo of his own voice because

  of the weakening in the air path.

  Control circuits are known for

  talking hands-free conversations.

  Thus, for example, the German patent application 24 39 740 discloses a device for voice-free hands-free conversation apparatus, which derives the control criteria for switching on and off the attenuation devices from the levels of speech voltage and guarantees a partial coupling of the weakening elements This requires for each channel and each direction of conversation a large number of organs

  weakening to obtain increases in

in small steps.

  The patent application R F A 27 14 132 describes a

  loudspeaker telephone apparatus which, for the

  transmission channel, has a multi-position switch which also

defined attenuation levels.

  By the patent application R F A 27 10 816, it is

  known to use individual control amplifiers

  channel duels for the switching of

  this arrangement-preventing an overexcitation

  loudspeakers and therefore also a

  mutation from operation to receiver in operation -3-

in transmitter.

  These known devices require the implementation

  many weakening bodies and organizations

  of adjustment which must be partly

  These devices require moreover

  a quick recognition of a voice signal, a determination

  sure nation of the sense of conversation, a connection

  constant for the duration of the conversation and a com-

  rapid change when the other party starts to speak and low thresholds of reaction of the control device by voice As a result of the incomplete decoupling of the transmission paths of known type of hands-free conversation systems, exceeding the threshold of

  reaction does not yet give a distinct signal of change.

  Conversely, the transmission signal reaches the weakening of the terminator

  in the reception part and exceeds the threshold of

  On the other hand, the transmitter stage can not, by the level, distinguish between the reception signal sent by

  the speaker and a voice signal from the user.

  It is an object of the present invention to provide a hands-free conversation device which completely suppresses the echo, enables a secure identification of the

  meaning of the conversation, ensures a practical

  without delay in the event of a change in the meaning of the con-

  and guarantees a constant level curve at the connection state of the hands-free conversation device.

  According to the invention, the transmission signal is in-

  jected through a resistor in the coil.

  secondary signal and the reception signal

  is collected on the transverse branch of the bridge of the

  minor The three states of operation -emission, re-

  pos and reception are determined for constant level increases and decreases which are produced by two amplifier switching amplifiers -4-

  transmitter and two weakening devices of amplifi-

  receiver and are controlled by amplifiers

  regulators and level detectors By means of the de-

  level sensors, a sequence of processes is determined.

  above switching for the identification of the meaning of the

  conversation that command, through

  a locking of each operating state

  mentally, the removal of a lock being triggered

  according to the time constants of the detectors

level.

  The invention will be better understood using the

  description of an embodiment taken as an example

  non-limiting and illustrated by the attached drawing, on the-

  which figure 1 represents a block diagram of the

  positive hands-free conversation and Figure 2 the

control circuit of the terminator.

  Level differences in the direction of

  sion and reception are decisive for the im-

  subjective hearing pressure, for the device of con-

  pouring hands free according to the invention is provided

  three defined levels or operating states, the

  calves listed below which may also be

  values, but always three precise fixed values.

  During the transmission, the amplification increases by 9 dB relative to the amplification of rest of the transmitter stage, while the amplification at the reception is decreased by 12 dB relative to the amplification of rest. of the receiver stage The increase of the amplification at the emission is knowingly kept lower than the

  decrease in amplification at reception An increase in

  the amplification at issue equal to the decrease

  -ion of amplification at the reception would be distinct-

  heard by the other party.

  The reception state of the conversation device

  free hands is characterized by the increase of

  the amplification of reception of 12 d B with decrease si-

  - multi-level of amplification at the emission of 12 d B Thus,

  for the other party, the echo is constantly

  of a defined value, for example 12 d B when switching from reception operation to the home position.

  The operation in emission and the functioning

  receiving position from the home position, are controlled after identification of a voice level and the direction of the conversation, by the control device by

  the voice as described in detail below with the aid of the

my synoptic according to Figure 1.

  During an interruption of the conversation, the

  hands-free conversation device occupies the posi-

  quiescence in which the amplification on transmission is reduced by 9 d B to take the idle value, while the amplification on reception takes the value -12 d B In such a case, the amplification on the reduced emission

  9 d B of the hands-free talking device suf-

  to communicate with the other party, so that the distance between the hands-free user and the microphone M of the hands-free conversation device can be variable without interrupting the conversation A direct transition from the transmission state the receiving state only occurs if, during a conversation, when one party is silent, the other party speaks directly. The amplification on reception is performed by two switching amplifiers SV 1, SV 2 whose amplification rates can be switched between two values

  by binary control signals The first amplifier

  Switching factor S Vl between the values Vl and V 2

  12 d B and the second switching amplifier SV 2 between

the values V 2 + 9 d B and V 2.

  Adjustment amplifiers RV 1, RV 2, RV 3

  operate as level regulators with

  limited level

  As a matter of fact, the response threshold, the response time constant and

  the holding time constant of these stages.

  The second adjustment amplifier RV 2 is used to balance the attenuation during reception operation. The level increase is, for example,

  d B The response time constant is chosen relative to

  tively large to prevent a "closure" of the

  reception by short-term peaks.

  With a great time keeping constant,

  for example 10 s, we get a regular curve of

  calf in the reception direction To adjust the

  sound on reception, the rate can be varied

  amplification of the EV adjustable amplifier

  within a certain range, or vary it in

  several steps by means of a switching amplifier

controlled by a key.

  The transmit signal for voice control is collected behind the first amplifier of

  SV 1 switching In reception operation, the first

  SV 1 switching amplifier weakens the 12 d signal B The first RV 1 amplifier is used to evaluate the noise in the transmit direction In case of loud noise on the speaker side

  hands free, the response threshold of the first amplifier

  setting factor RV 1 is exceeded and the amplification

  This results in an unresponsive response sensitivity.

  With the help of the large time constants in the control circuit, the stage forms an average value of the ambient noise. To guarantee, even in the case where the

  first amplifier amplifier RV 1 is "closed", the

  wise in emission position, the level rise is re-

pick at 9 d B.

  In case of activation of the first business unit

  DG 1 or the second weakening element DG 2, the levels are respectively lowered by 12 dB in

  receiving amplifier On the receiving side, the

  voice control process deals with different signals

  amortized in the signal path The first

  reception signal is collected behind the first attenuation element DG 1 and corresponds in its processing to the signal on the transmission side The third adjustment amplifier RV 3 sets the response sensitivity of the device

  voice control in the receiving direction

  Received Level The level increase is limited here to 12 d B.

  The second transmission signal is collected

  the final stage ES Its level therefore depends on the

  the sound intensity potentiometer of the ampli-

  adjustable EV controller and switching state of the second

weakening element DG 2.

  In the block diagram according to FIG. 1, the voice control device is symbolized by the level detectors PD 1, PD 2, PD 3 and the gates Gi,

G 2, G 3.

  As already mentioned at the beginning, a quick identification

  speech, the sense of the conversation, a constant connection during a conversation and an instantaneous switching as soon as the other speaker speaks, are the essential conditions

control device by voice.

  To guarantee an exact determination of the meaning

  of the conversation, according to the invention, the

  level PD 1 to PD 3 in a given order and

  performs a reciprocal locking of the operating states

  of the hands-free conversation device in

  the voice control device, the transmission signal

  is applied to the first PDI level detector, the first receive signal to the second level detector

  PD 2 and the second receive signal at the third detection

  PD level switch 3 These level sensors PD 1 to PD 3 8 -

  produce binary output signals after exceeds

  When the threshold voltage is reached, a logic "" appears at the output of each PD level detector. The corresponding level detector reacts with a certain delay which depends on its response time constant t A If one goes below of the threshold voltage, it appears at

  after a certain period of delay determined by the

  aunt of holding time, a logical "O" at the exit of the

  PD level detector The response time constants

  PD-PDI level detectors are established from

  to satisfy the inequality t A 3 <t Al <t A 2.

  In the rest position, that is, in the absence of

  of any transmission or reception signal, a logic level "O" appears at the output of each level detector P D L PD 3 The control outputs S, E for the hands-free telephone conversation device,

  take the state S = O, E = O (Figure 1).

  When the user speaks in the microphone M, the

  transmission signal exceeds the threshold in the first detection

  At the same time, the voice signal

  comes through the GA terminator on the receiving stage of the

  handsfree phone and activates the second

  level sensor PD 2 At rest position and in po-

  transmission, the second reception signal is

  less than 12 d B by the weakening element DG 2 The response threshold of the third level detector PD 3 is

  calculated so that it can not be exceeded at

  firing of the transmitter stage, even in the event of weaker termination of the terminator Thus, the first gate G1 remains constantly open in the event of reaction operation. If simultaneous activation of the first and second level detectors, PD 1, PD 2, the priority in time, resulting from t Al <t A 2, the first detector of

  level P Dl causes a safe switching of the status of re-

  pos S = 0, E = O at the emission position S = 1, E = O In fact 9 -

  the locking of the third door G 3, the operation

  The transmission state remains maintained independently of the output state of the second level detector PD 2, until the output of the first PD level detector 1 has a logical "O". In transmission operation, the reception signals are weakened by the first

  DG 1 at the input of the reception channel.

  As a result of this further weakening, the

  transmission caliber reaching the receiver amplifier EV via the GA terminator is no longer sufficient to activate the second level detector PD 2. In the direction of transmission, it is therefore only possible to distinguish between operation in emission and rest position with a rise of amplification of 9 d B.

  The signal level of the other party

  the GA terminator, on the other hand, goes beyond the transmission mode of the telephone device

  hands-free threshold voltage, reception side, of the two-

  th PD 2 level detector and activates the latter Already

  brief interruptions in the output signal of the first

  first level detector P D1 then provoke by the de-

  locking the third door G 3, a switching

  immediately from the transmission position S = 1, E = O to the posi-

  reception S = 0, E = 1 A direct change of meaning

  conversation is also possible in case of

  wise from the reception position to the transmission position.

  In principle, in the same way, as long as the third level detector PD 3 remains inactive, the two interlocutors have the same right to

speak.

  In the case of good communications, the reception signal emitted by the loudspeaker L and the voice signal of the speaker speaking the handsfree reach substantially the same levels. The reception signal can then, from the rest position, activate the first level detector PD 1 emission side In this case of operation, a faulty switch in the

  sense of reception is prevented by the third detection

PD level 3.

  Sizing of the response threshold of the third

  PD 3 level detector is determined by the level of re-

  ception necessary for the activation of the first PD level detector 1 Given the anti-whistle safety

  required for a hands-free telephone device (am-

  circuitry <1) this level can not be exceeded

  receiving signals In such a case, the

  PD 1 PD 3 level sensors are activated simultaneously.

  The switching of the transmission channels results from the

  succession in time of the signals of the detectors of

  As a result of the priority t A 3 <t Ai, it is firstly the first gate Gi which is blocked and therefore the signal of the first level detector PD 1. The second level detector PD 2 then establishes the operation.

in reception S = 0, E = 1.

  As the response threshold of the third

  The third level detector PD 3 necessarily provokes the

  switching in the receiving direction, the other

  the speaker has priority vis-à-vis the interlocutor

hands free.

  The operation of the hands-free telephone device depends essentially on the observation of the level increases in the transmission channels and the response thresholds within the device.

  voice control To allow power to be

  the connection lines a, b, it is at the same time necessary to provide a reduction in the consumption of the quiescent current of the entire hands-free telephone device. It is for this reason that operational amplifiers are used. low power for the signal path Switching or adjustment of the amplification of the different stages is controlled by N-channel field effect transistors. As an end stage, an integrated circuit is used which is characterized by a low quiescent current and a reduced implementation of external components Behind the output of the final stage, the speaker level L

  is weakened by 6 d B by a resistance.

  cording of an additional loudspeaker, we obtain an ambient sound intensity gain of 6 d B.

  From the connecting lines a, b, the ter-

  according to Figure 2 provides the telephone device

  free hands via the rectifiers

  G 21, G 22 connected in parallel, the service voltage

  vice UB which is limited to a value determined by a

  Zener diode G 20 The UV supply voltage for the

  the final ES of the hands-free telephone system is

  collected on the positive half-bridge of the rectifier G 22.

  This parallel power supply of the final stage ES is ef-

  performed to prevent coupling of the

  ception at the SE input are only via

  of the service voltage line on the amplifier input

* Fier transceiver.

  In this terminator, the directions of transmission and re-

  ception are inverted with respect to

  classical phonics; the SS transmit signal is injected

  by a resistor R 20 in the secondary winding of the transformer UE The voltage supply and the reception of the reception signal SE are in the transverse branch of the bridge As a complex balancer for the characteristic impedance, the combination R 21, R 22, C 20

  cooperates with the resistance of the winding of the

  EU adapter which is connected to the resistor R 21

  ge saves an additional transformer for repairing

send the reception signal SE.

  If the connection lines a, b are interrupted by triggering the hands-free conversation actuator or during the dialing of the 12-number, the terminator is not isolated on the input side and the SS transmission signal is completely injected into the receiver amplifier constituted by the amplifier

  adjustable E Vf the final stage ES, the weakening

  associated DG 1, DG 2 and the RV 2, RV 3 tuning amplifiers of the hands-free

  capacitance C 21, C 22, the capacitors

  UV and UG positive service levels only decrease

  Thus, a reaction hiss may occur just after the interruption of the loop. To avoid this, any oscillation primer is prevented by a transistor.

  field effect at the input of the receiver amplifier.

  A power-off signal SL, which, in case of a

  loop through the terminator appears as a negative operating voltage UB at the rectifier

  in bridge G 22, closes the input transistor of the ampli-

  receiver-receiver If the loop current is interrupted,

  that is to say interruption of the connection lines a, b, the bridge rectifier G 22 is no longer traversed by the current

  and the input transistor bypasses the input of the am-

plificateur receiver. 13 -

Claims (11)

  1. Control circuit for a control device   hands-free in telephone installations   including a 2-wire-4-wire terminating circuit, an identification of the direction of conversation, controlled by the   voice and a switching device for amplifiers   transmitters and receivers whose criteria for   for the switching on and off of   weakening are derived from the voltage levels   telephony, characterized in that the broadcast signal   sion (SS) is injected by a resistor (R 20) into the   Secondary end of the terminator (UE) and the reception signal (SE) is collected on the transverse branch   of the terminator bridge, that three states of operation -   emission, rest and reception are determined by   constant levelings or decreases that are produced by two switching amplifiers (SV 1,   SV 2) of the transmitter amplifier and two   (DG 1, DG 2) of the receiver amplifier and are controlled by control amplifiers (RV 1, RV 2, RV 3) and level detectors (PD 1, PD 2, PD 3), and the level detectors (PD 1 PD 2, PD 3) establish a switching sequence for identifying the direction of the conversation which, via gates (Gi, G 2, G 3), control a lock of each state of   operation, the removal of a lock being de-   triggered according to the time constants of the detec- level.   2. Control circuit according to claim 1, characterized in that the terminator comprises two bridge rectifiers (G 21), (G 22) in parallel, a Zener diode (G 21) being connected in parallel with the first of these rectifiers to limit the operating voltage (UB) to   a value subject to only minimal variations,   say that the second rectifier supplies the power supply   (UV) for the final stage (ES) of the con- 14 -   hands-free delivery and a food stop signal   (SL) to block the receiver amplifier when   that the terminator is not isolated on the input side.   Control circuit according to Claim 1, characterized in that the transmitter amplifier consists of two switching amplifiers (SV 1, SV 2), an adjusting amplifier (R Vl) and a signal detector. level (PD 1).   Control circuit according to Claim 1, characterized in that the receiver amplifier consists of two weakening elements (DG 1, DG 2),   two control amplifiers (RV 2, RV 3), an ampli-   regulator (EV), a final stage (ES) and two level sensors (PD 2, PD 3).   Control circuit according to Claim 1, characterized in that the control amplifiers   (RV 1, RV 2, RV 3) function as a regulator of   calf with a limited increase and whose thresholds   response time constants and the constants   time can be set independently. from each other.   6. Control circuit according to any one of   claims 1, 3, 5, characterized in that for   the transmission operation of the translation device   In the hands-free mode, the transmission signal is collected behind the first switching amplifier and, via the first control amplifier (RV 1).   and the first level detector (PD 1) controls the   rusting of the third door (G 3).   7 Control circuit according to any one of   claims 1, 4, 5, 6, characterized by the fact that   level of signal arriving through the terminator (GA) and   the threshold voltage, on the receiving side, of the second de-   level sensor (PD 2), controls the locking of the   second door (G 2) and switches the conversation device   hands-free operation on receiving operation.   - 8. Control circuit according to any one of   claims 1, 4, 5, 6, 7, characterized by the fact   that the response threshold of the third detection   level switch (PD 3) causes switching of the   tif conversation hands-free in the receiving direction,   while the first door (Gi) is blocked.   9. Control circuit according to any one of   claims 1, 4, 5, 6, 7, 8, characterized by the fact   that the response time constants (t Ai, t A 2, t A 3) of   level detectors (PD 1 PD 2, PD 3) satisfy the inequality t A 3 <t Al <t A 2.   10. Control circuit according to claim 1, characterized in that for the signal processing, the hands-free conversation device comprises   low power operational amplifiers.   11. Control circuit according to claim 1,   characterized in that for switching or resetting   of the different amplifier stages, the hands-free conversation device comprises N-channel field effect transistors.