JPS622499B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a telephone communication device, which realizes a more natural telephone conversation by switching to the receiving state when the caller stops transmitting even if the receiving signal is small. The purpose is to

Conventional communication equipment uses a variable loss circuit that can adjust the amplification degree for the transmitting and receiving systems, and compares the transmitting level and the receiving level, and then compares the comparison output with the output at the time of transmitting and receiving. A control circuit that controls the amplification degree of the variable loss circuit according to an output compared with a predetermined value, and a reception signal is applied to the control circuit via the variable loss circuit when transmitting or receiving a call. Alternatively, the communication device is equipped with a switching means for selecting whether to apply the signal directly without passing it through the variable loss circuit, and obtains the receiving system input that is applied to the AC compression circuit directly from the hybrid transformer when sending and receiving a call. At the same time, the received signal obtained from the receiving system and the transmitting system signal are compared to control the loss amount of the variable loss circuit provided in the transmitting system and the receiving system. That's what I do.

However, in this case, if there is noise on the transmitting side and the received signal is small, the received signal from the hybrid transformer in the transmitting state will be greatly influenced by the sidetone of the transmitted signal, and the received signal will be buried in the sidetone. There are disadvantages in terms of call quality, such as being unable to make a call or often cutting off the beginning of a conversation when receiving a call.

The present invention eliminates these drawbacks. An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a block diagram of a communication device which is an embodiment of the present invention, FIG. 2 is a partial circuit diagram of an amplifier of the same device, and FIG. 3 is a timing chart of outputs of various parts of the device. In the figure, 1 is a microphone, 2
is a speaker, 3, 4, 5, 6 is an amplifier, 7, 8 is a variable loss circuit, 9 is a hybrid transformer, 10
11 is a transmitting signal input circuit, 11 is a receiving signal input circuit,
12 is a differential amplifier, 13 and 14 are differential amplifiers 12
The comparator 15 compares the output of the variable loss circuits 7 and 8 with the set values S ₁ and S ₂ respectively.
Flip-flops 16 and 17 are switches that are turned on and off in accordance with the output of flip-flop 15. 1
8 is a switching transistor 19 is a time limit circuit;
20 is a DC bias circuit consisting of a resistor and a bias power supply, and 21 is a control terminal.

It is assumed that the time limit circuit 19 performs its original operation (has a delay time) only when the control terminal 21 is at the "H" level, and has no delay time when the control terminal 21 is at the "L" level.

It is also assumed that the switch 17 receives the Q output of the flip-flop 15 only when the control terminal 21 is at the "L" level, and is forcibly turned off when it is at the "H" level.

The switching transistor 18 is connected to the control terminal 21
is turned ON when the signal is at the "H" level, and a DC bias circuit 20 is connected to the received signal input circuit 11 to apply a constant bias.

Fig. 2 shows the relationship between the volume adjuster 61 and the control switch 62 provided in the amplifier 6 (or in the receiving system). Control switch 6 from point
2 is turned ON and the control terminal 21 is set to "H" level. If it is below the specific point, the same switch 62
When it is OFF, the control terminal 21 is set to "L" level.
(It goes without saying that the switch 62 may be set to "L" level when it is turned on, and set to "H" level when it is turned off.) Next, the operation of the communication device based on this configuration will be explained. First, when the volume determined by the volume adjuster 61 is lower than a specific level (when the control terminal 21 is set to "L"), the switch 17 is turned on and off based on the output of the slip-flop 15.
While operating, the switching transistor 18
It is in the OFF state and performs the same switch action as a conventional switch.

Under these conditions, A. When the communication path loss is large, _A.sub.1 ...When the line length is long, the received signal becomes small.

A ₂ ...During a conference call, the impedance decreases and the received signal becomes weaker.

B: When the ambient noise is large, the receiving signal is too low compared to the transmitting audio level, making it difficult to receive good reception.

Therefore, at this time, the volume of the receiving system must be adjusted. The present invention focuses on this point, and adjusts the volume adjuster 61 so that when the volume controller 61 is set to a position corresponding to a level higher than the level corresponding to a specific level position, an "H" level is applied to the control terminal 21. The switch 17 is forcibly turned off by the switch 17, while the switching transistor 18 is turned on so that a constant bias is applied to the reception signal input circuit 11.

Therefore, the DC bias circuit 20 is connected to the switching transistor 18 in the reception signal input circuit 11 during transmission.
Since the receiving signal input circuit 11 is connected through the terminal, a constant bias is applied to the receiving signal input circuit 11 even if there is no output from the amplifier 6. Therefore, the output of the transmitting input circuit 10 is R _T , the output of the receiving signal input circuit 11 is R _R , and the setting value
When S ₂ is set to -T, the transmitted voice becomes small and R
When _T /R _R <-T becomes R _T /D <-T, the output of the comparator 13 becomes "H" level, and the state is switched to the receiving state.

At this time, a time limit circuit 19 is inserted between the comparator 14 and the flip-flop 15, and holds the transmission switching signal for the time set by the time limit circuit 19.

In Figure 3, A is the output of comparator 14, and B is the output of comparator 1.
3, which is the output from the set terminal S of the flip-flop 15 when the control terminal 21 is at the "L" level.
, and d shows the output of the same output terminal Q. In this case, the control terminal 21 is “H” and the time limit circuit 1
9 shows the input to the set terminal S of the flip-flop 15 when the flip-flop 15 is inserted, and also shows the output from the output terminal Q to the flip-flop 15. The time T _D is the operation delay time, and T _D1 is the transmission holding time.

Further, by providing the timer circuit 19 in this manner, the switching from transmitting to receiving can be delayed by a certain period of time T _D , thereby preventing unpleasant end-of-word interruptions during a telephone call.

As described above, according to the present invention, when the receiving input signal is small, by setting the adjusting section of the receiving volume adjuster to a level position corresponding to a level higher than a level corresponding to a predetermined level position, the amplification degree is increased and the signal is transmitted. Since the switching between speaking and receiving is performed by the magnitude of the transmitting level, it is possible to completely prevent the malfunction of switching between speaking and receiving that occurs when the received voice is amplified to make it easier to listen to, as in the conventional case.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a communication device according to an embodiment of the present invention, FIG. 2 is a detailed view of the same part, and FIG. 3 is a timing chart of the same. 1...Microphone, 2...Speaker, 3, 4, 5,
6...Amplifier, 15...Flip-flop, 1
6, 17... Switch, 18... Switching transistor, 19... Time limit circuit, 20... DC bias circuit, 61... Volume adjuster, 62... Control switch.

Claims (1)

[Claims] 1. A variable loss circuit that is connected to the transmitting system and the receiving system and can adjust the amplification level, and a variable loss circuit that is connected to the transmitting system and the receiving system, and a variable loss circuit that can adjust the amplification level according to the output that compares the transmitting level and the receiving level with the predetermined value at the time of transmitting and receiving. and a control circuit for controlling the amplification degree of the variable loss circuit, a receiver volume adjuster connected to the receiver system, and an adjustment section for adjusting the receiver volume level of the receiver volume adjuster corresponding to a predetermined level position. When the device is at a level position corresponding to a level smaller than the level to be used, the transmitting and receiving signals are switched based on a comparison output between the transmitting level and the receiving level, and the level position corresponding to a level higher than the level corresponding to the predetermined level position is reached. The communication device is provided with a selection circuit for switching between transmitting and receiving depending on the magnitude of the transmitting level regardless of the magnitude of the receiving level.