JPH0865364A - Terminal connection device - Google Patents

Abstract

PURPOSE: To stabilize a telephone communication by setting current detection sensitivity low so that a telephone set is a little affected by a signal driving a speaker and an external noise in its stand-by state, and putting the detection sensitivity back to stationary one after hook-up operation. CONSTITUTION: A current sensitivity switching circuit 46 which switches the current detection sensitivity of a current detecting circuit 42 is provided in the terminal connecting device 4. When the telephone set 1 is in the standby state, no speaking current flows, so the circuit 42 does not detect any current sets a relay 43 so as to a signal transmission line 3 to the sound source 5 for a speaker through a speaker connecting circuit 44, and the sound source 5 drives the speaker 2. Further, the circuit 46 sets the detection sensitivity of the circuit 42 low. When the telephone set 1 is placed in the on-hook state, a speaking current flows, so the circuit 42 detects that and forms a channel by setting the relay 43 so that the transmission line 3 is connected to a line switching circuit 6 through a telephone set connecting circuit 45, and the circuit 46 puts the sensitivity of the circuit 42 back to stationary one.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terminal connecting device in a main unit of a circuit switching device connected to both a telephone and a speaker.

[0002]

2. Description of the Related Art FIG. 3 shows a configuration of a terminal connection device of a line switching main device B which is connected to a telephone which is a conventional accommodation terminal A and a speaker. Here, 1 is a telephone, 2 is a speaker, 3
Is a signal transmission path (hereinafter referred to as a transmission path), 4 is a terminal connecting device, and 5 is a speaker sound source. Reference numeral 6 is a circuit switching network, through which the terminal connection device 4 is connected to other terminal connection devices and office line connection units. When the telephone 1 is not used, only the speaker 2 serves as the terminal of the terminal connecting device 4. Since the telephone 1 does not flow a call current in the on-hook state (hook-down state), the current detection circuit 42 of the terminal connection device 4 does not detect the current, and the transmission path 3 is connected to the speaker sound source 5 through the speaker connection circuit 44. The relay 43 is set so that the speaker sound source 5 drives the speaker 2. Here, the speaker sound source 5 is a tape recorder, a broadcasting microphone, or the like. When the telephone 1 goes into the off-hook state (hook-up state), the telephone 1 becomes a terminal of the terminal connecting device 4 in addition to the speaker 2, and a call current flows through the transmission path 3, so that the current detecting circuit 42 of the terminal connecting device 4 turns it on. The relay 43 is detected and the relay 43 is set so as to connect the signal transmission path 3 to the circuit switching network 6 through the telephone connection circuit 45, and a communication path is formed. At this time, since the speaker 2 cannot be driven at the level of the signal handled by the telephone 1, the speaker 2 can be ignored.

[0003]

The telephone and the speaker are often used at positions far away from the circuit-switching main unit, and the transmission path is considerably long, which increases the possibility of being affected by external noise. In the conventional device, generally, when the telephone is in the standby state (on-hook state), if the detection sensitivity of the call current is set low so as not to erroneously detect the signal for driving the speaker and the external noise as the call current, the device shifts to the call state. Later, when the call current has no margin with respect to the set value, the detection becomes unstable, and the relay malfunctions and the call is interrupted.

The present invention provides a terminal connecting device which can perform stable operation in both a standby state and a call state.

[0005]

In order to solve this problem, in the terminal connecting device according to the present invention, the detection sensitivity of the call current is set low when the telephone is in the standby state, and when the telephone is hooked up. It is configured to detect the current flowing in the transmission path and switch the relay from the speaker connection circuit to the telephone connection circuit to form a communication path, and to return the current detection sensitivity to the steady state.

[0006]

According to the present invention, when the telephone is in the standby state, the current detection sensitivity is set low so as not to be easily influenced by the signal for driving the speaker and the external noise, and the current detection sensitivity is returned to the steady state after the hookup. As a result, it is possible to operate so as to keep the communication state stable against variations in the impedance of the connected transmission line and telephone.

[0007]

FIG. 1 shows the configuration of an embodiment of a terminal connecting device according to the present invention connected to a telephone and a speaker. here,
1 is a telephone, 2 is a speaker, 3 is a signal transmission path, 4 is a terminal connection device, 5 is a speaker sound source, and 6 is a circuit switching network. In the present invention, the terminal connection device 4 is provided with the current sensitivity switching circuit 46 for switching the current detection sensitivity of the current detection circuit 42. When the telephone 1 is in the standby state, the current detection circuit 42 of the terminal connection device 4 does not detect the current because the call current does not flow, and the signal transmission path 3 is connected to the speaker sound source 5 through the speaker connection circuit 44. The relay 43 is set to, and the speaker sound source 5 drives the speaker 2. Further, the detection sensitivity of the current detection circuit 42 is lowered by the current sensitivity switching circuit 46. When the telephone set 1 goes off-hook (hook-up), a call current flows, which is detected by the current detection circuit 42 of the terminal connection device 4, and the signal transmission path 3 is passed through the telephone connection circuit 45 to the line switching circuit network 6
The relay 43 is set so as to be connected to the line 43 to form a communication path, and the sensitivity of the current detection circuit 42 is returned to the steady state by the current sensitivity switching circuit 46.

[0008]

[Table 1]

FIG. 2 shows a concrete example of the current detection circuit 42, the relay 43, and the current sensitivity switching circuit 46 inside the terminal connection device 4, and Table 1 shows each part of the comparison circuit in the current detection circuit 42 corresponding to the hook state. Indicates electric potential. L of the transmission line connection terminal 41
A telephone 1 is connected to 1 and L2 through a signal transmission line 3, and a call current is supplied from a power source VA (not shown) to a resistor R1, a signal transmission line L1 (forward), a telephone 1, and a signal transmission line L2.
(Return), flows through the resistors R2 and R3 and flows into the ground. The detection input voltage VD generated between the terminals of the resistor R3 is obtained by comparing the power supply voltage VA with the resistors R4, R5, (R6) by the comparison circuit composed of the transistors T1, T2 and the resistors R7, R8, R9.
The voltage is compared with the reference voltage VE divided by, and the relay 43 and the current detection sensitivity are controlled according to the comparison result (Table 1).
Here, C1 is a capacitor that bypasses the AC component so that the signal component is not superimposed on VD. When the telephone 1 is in the standby state (on-hook), the call current does not flow, the detection input voltage VD is 0 V, and the reference voltage VE has a higher potential, so the transistor T2 is turned off. Therefore, since no current flows through the resistor R9, the transistor T3 is also turned off, and the reference voltage VE changes the value of the detection input voltage VA to the resistance R4.
And the value divided by R5 remains, and the sensitivity of the current detection circuit 42 decreases. When the telephone hooks up, a call current flows. Therefore, when the value of the detected input voltage VD rises and exceeds the value of the reference voltage VE, the transistors T2 and T3 are turned on, and as shown in Table 1, the value of the reference voltage VE becomes Power supply voltage V
A is switched to a value divided by resistors R4, R5, R6,
The sensitivity of the current detection circuit 42 is in a steady state. At this time, the reference voltage VE is lower than before as compared with the detection input voltage VD, and even if the call current is slightly reduced, VD
Is less likely to be lower than VE, and stable operation can be secured even if the impedance of the telephone 1 is slightly changed.

[0010]

As described in detail above, according to the present invention, the terminal connection device has a speaker connection circuit, a telephone connection circuit, a means for switching between them, a current detection circuit, and a current sensitivity switching circuit. Then, when the phone hooks up, the current flowing in the transmission line is detected, the transmission line is switched from the speaker connection circuit to the telephone connection circuit, and the current detection sensitivity is switched, so that the speaker is driven when the phone is in the standby state. It is possible to make it less susceptible to external signals and external noise, and to keep the operation stable after the hook-up even against changes in the impedance of the connected transmission line or telephone.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of a current detection circuit, a relay, and a current sensitivity switching circuit used in the present invention.

FIG. 3 is a block diagram showing a conventional terminal connection circuit and peripheral circuits.

[Explanation of symbols]

1 Telephone 2 Speaker 3 Signal Transmission Line 4 Terminal Connection Device 5 Speaker Sound Source 6 Circuit Switching Circuit Network 41 Transmission Line Connection Terminal 42 Current Detection Circuit 43 Relay 44 Speaker Connection Circuit 45 Telephone Connection Circuit 46 Current Sensitivity Switching Circuit R1, R2, R3 , R4, R5, R6, R7, R8, R
9 Resistance C1 Capacitor T1, T2, T3 Transistor

Claims (1)

[Claims] 1. A telephone and a speaker arranged on one end side of a signal transmission line, and a circuit switching main unit arranged on the other end side of the signal transmission line via the signal transmission line, wherein: A speaker connection circuit that handles a signal to the speaker, a telephone connection circuit that handles a signal to the telephone, a current detection circuit that detects a call current flowing through the signal transmission path, and a current A sensitivity switching circuit that switches the current detection sensitivity of the detection circuit; and a switching unit that controls switching between the speaker connection circuit and the telephone connection circuit by detecting the call current by the current detection circuit. In this case, the current detection sensitivity is set low so as not to erroneously detect a signal for driving the speaker or an external noise as the call current. When the speaker goes off-hook, the call current flowing through the signal transmission path is detected to switch from the speaker connection circuit to the telephone connection circuit, and the current detection sensitivity is switched to a steady state. Terminal connection device.