JPH063951B2 - Loud phone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention has a loudspeaker function, and a push button signal (P
The present invention relates to a loudspeaker telephone (generally called a push-button speakerphone) that uses B signal) as a selection signal.

2. Description of the Related Art Generally, a loudspeaker telephone is a voice switch system. In this voice switch system, as shown in FIG. 2, a transmission signal and a reception signal are compared with each other, and during transmission (sending signal> reception signal), a reception suppressing circuit 3 for suppressing the reception signal, during reception (sending signal <sending signal < (Received signal)
Is a transmission suppression circuit 6 for suppressing the transmission signal, and a control signal 9a corresponding to each state by comparing the transmission signal and the reception signal.
The control circuit 9 controls the transmission suppression circuit 3 and the reception suppression circuit 6 at 9b. A hybrid circuit 2 for separating a transmission signal and a reception signal is coupled to the telephone line terminals 1a and 1b, and a reception signal 2a from the hybrid circuit 2 is applied to a reception suppression circuit 3 and a control circuit 9 to suppress the reception. The received signal that has passed through the circuit 3 is amplified by the amplifier 4 and drives the speaker 3. On the other hand, the transmission signal from the microphone 8 is amplified by the amplifier 7 and added to the transmission suppression circuit 6 and the control circuit 9, and the transmission signal passing through the transmission suppression circuit 6 is transmitted to the hybrid circuit 2 as the transmission signal 2b. Added. Further, the PB signal from the PB signal generating circuit 11 which operates according to the operation of the keyboard 12 is amplified by the amplifier 10 and
The B signal 11a is added to the hybrid circuit 2.

Now, when the push button of the keyboard 12 is pushed while the loudspeaker function is off-hook using the telephone, the PB signal generating circuit 11 generates two kinds of AC signals, PB signals corresponding to the numbers, and sends them to the telephone line. In the case of transmitting the PB signal in this manner, the PB signal is generated by detecting that the button is pressed, amplified, and then transmitted through the hybrid circuit 2 for separating the transmission signal and the reception signal.

The problem to be solved by the invention is that, in the conventional method, the degree of separation of transmission / reception of the hybrid circuit 2 does not become infinite due to variations in the AC impedance of the telephone line and variations in the input AC impedance of the telephone side, and the reception There was a problem that the PB signal leaked out from the speaker 5 through the system.

The present invention is intended to provide a loudspeaker telephone capable of alleviating and eliminating such a problem and capable of excellently transmitting a PB signal with a simple circuit.

Means for Solving the Problems The present invention treats the PB signal as a transmission signal,
The B signal is input to the control circuit, the reception suppressing circuit is operated by the control signal from the control circuit, the PB signal leaking through the hybrid circuit is suppressed, and the leak output of the PB signal from the speaker is suppressed.

Action The present invention operates the reception suppressing circuit with the PB signal, so that there is no need for a special auxiliary circuit for suppressing the leakage output.
Even when it is desired to output the B signal as a monitor sound, a clear monitor sound can be obtained without being mixed with the leak signal by inputting the monitor sound after the reception suppression circuit.

Embodiment An embodiment of the public address telephone of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of an embodiment of the public address telephone of the present invention. 1 is different from FIG. 2 in that the PB signal 11a is added to the control circuit 9 and the transmission suppression circuit 6. The voice amplification function compares the received signal from the telephone line with the transmitted signal from the microphone as in the conventional one, and the control signal 9 from the control circuit 9 according to the comparison result.
This is realized by operating the reception suppressing circuit 3 and the transmission suppressing circuit 6 by a and 9b. Keyboard 12 now
Press one of the numbers on the push button of the PB signal generation circuit 1
PB signals, which are two types of AC signals corresponding to numbers, are generated from 1, and are amplified by the amplifier 10 and input to the control circuit 9 as a transmission signal. Since the control circuit 9 tries to make a call when the push button is pressed, it can be determined that there is no reception signal, and the reception suppression circuit 3 is controlled by the control signal 9a which is the comparison result of the transmission signal and the reception signal. To operate.

The PB signal, which is a transmission signal, is transmitted to the telephone lines 1a and 1b and cannot be separated by the hybrid circuit 2.
Even if the B signal leaks to the receiving system, it is suppressed by the receiving suppression circuit 3 and is not output to the speaker 5.

EFFECTS OF THE INVENTION As described above, according to the present invention, the PB signal is treated as the transmission signal and is input to the control circuit for comparing the transmission signal and the reception signal, and the reception suppression circuit is operated by the control signal from the control circuit. By doing so, it is possible to prevent the PB signal from leaking to the receiving system.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a loudspeaker telephone of the present invention, and FIG. 2 is a block diagram of a conventional loudspeaker telephone. 1a, 1b ... telephone line, 2 ... hybrid circuit, 3
...... Reception suppression circuit, 5 ... Speaker, 6 ... Transmission suppression circuit, 8 ... Microphone, 9 ... Control circuit, 11 ... P
B signal generation circuit, 12 ... Keyboard.

Claims (1)

[Claims] 1. A loudspeaker telephone using a push button signal as a selection signal, wherein a push button is used as a transmission signal of a control circuit for comparing a reception signal and a transmission signal as an input signal to turn on / off a reception suppression circuit and a transmission suppression circuit. A loudspeaker telephone characterized in that the reception suppression circuit is operated by a signal from the control circuit during the transmission of the push button signal by using a signal.