JPS6156560A - Telephone circuit - Google Patents

Abstract

PURPOSE:To prevent the resonance of dial pulses due to the parallel connection of telephones for a telephone circuit, by using a detection circuit which detects that the applied voltage given from a telephone circuit is lower than a set level and delivers the result of this detection in an on-hook state of the telephone and a means which separates a bell from the telephone circuit with the output said detection circuit. CONSTITUTION:A telephone T1 (T2) is hooked off for dialing and therefore the voltage V between terminals L1 and L2 is usually lowered down to <=1/2 voltage VB of a battery B. While a DC circuit is not closed in an on-hook state of the telephone, and the voltage V between terminals L1 and L2 is equal to VB. Therefore it is decided that one or more telephones are hooked off in a state where the voltage V is reduced down to <=1/2VB. Then a detection circuit 5 works to separate a bell 4 from a telephone circuit A through a relay contact 7 for the telephone T2 set under an on-hook state. Therefore the dial pulses produced by the T1 are not applied to the bell 4. This avoids the resonance of dial pulses.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a telephone circuit, especially when two or more units are connected in parallel.
This invention relates to a telephone circuit that prevents a dial pulse transmitted by one telephone from operating the bell of one or more other telephones and generating a ringing tone.

(Prior Art) FIG. 2 shows a state in which a telephone mTt and a telephone T2 are connected in parallel to a telephone line operator. A direct fi voltage is always applied to the telephones TI and T2 from a trunk circuit constituted by a coil L of a telephone exchange S and a battery B. Conventionally, when the telephone TI goes off-hook and dials, the bell of the parallel-connected telephone T2 operates and generates a ringing tone, resulting in an inconvenience.

In other words, when one of the two telephones dials, it sends a dial pulse that cuts off the direct current in the telephone line at a rate of 10 or 20 times/second, and sends the dialed number to the telephone exchange. do. On the other hand, the phone is 16H
Since there is a function to notify the incoming call by making a ringing signal using an AC signal of There was a drawback: it made a ringing sound (hereinafter referred to as resonance).

In recent years, there has been a tendency to shift from electromagnetic bells to electronic bells, and electronic bells (such as the ML8204 manufactured by MI Okisha)
Circuits using ICs and speakers (such as circuits using ICs and speakers) have the disadvantage that they are particularly susceptible to resonance due to their high operating sensitivity.

The cause of resonance is that the frequency of the dial pulse is 10
Hz or 20 Hz, which is close to the 16 Hz of the ringing signal, causing the bell to malfunction.

(Object of the Invention) An object of the present invention is to provide a telephone circuit that prevents resonance due to dial pulses that occur when conventional telephones are connected in parallel.

(Structure of the Invention) According to the present invention, there is provided a detection circuit that detects and outputs when the voltage applied from the telephone line becomes lower than a preset voltage when the telephone is in an on-hook state; A telephone circuit is obtained, characterized in that it includes means for disconnecting from the line.

(Example) Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, in which terminals LL and L2 connected to a telephone line A, a hook switch l connected to the terminal L1, and an eye hook switch l are in an off-hook state (as shown in the figure). The bell 4 is connected via the relay contact 7 in the on-hook state, and the detection circuit 5 is connected to the terminal L1 in the on-hook state, and the DC voltage between the terminals L1 and L2 is in the on-hook state. When the DC voltage VB of the battery B becomes less than 1/2, the detection circuit 5 detects this and opens the relay contact 7.The relay 6 and the hook switch 1 are in an off footer state (x and y are closed). It is composed of a dial pulse transmitting circuit 2 that is connected at the time of , and a telephone call circuit 3 that is connected via the dial pulse transmitting circuit 2t.

Next, the operation will be explained. Now, when telephone Tl goes off-hook to dial (the same applies to telephone T2), terminal L
The voltage V between 1 and L2 is T: Direct current resistance of the telephone: Koi, n = LO DC resistance R MU2 Telephone circuit III Person's DC resistance vB: Voltage of battery B, AWL l-L 2nJFDIJIJE V
Has Vn C' l / 2 or less. Since the direct optical circuit is not closed when the telephone is on-hook, the voltage V between terminals Ll and LZ becomes the same as VB.

Therefore, in a state in which the value between m-devices Ll and Lz drops below 01kEtJzt/zVB, it can be determined that one or more telephones are in an off-hook state. Therefore, in the on-hook state of the telephone T2, the detection circuit 5 operates, and the bell 4t-! J-ray contact 7
Since the telephone T1 is disconnected from the telephone line A, the dial pulse generated by the telephone T1 is not applied to the bell 4, and no resonance occurs.

This operation is the same even when three or more telephones are connected in parallel.

Further, in the embodiment of the present invention, the bell is separated by a mechanical contact of a relay, but it is naturally possible to apply a semiconductor switch or the like.

(Effects of the Invention) As explained above, the present invention, when two or more telephones are connected in parallel, allows the other 11-phone telephone to dial by determining the voltage applied from the telephone line. By detecting this and separating the bell from the IL communication line, resonance of the bell can be prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of a general telephone set.

Claims (1)

[Claims] It is characterized by comprising a detection circuit that detects and outputs when the voltage applied from the telephone line becomes lower than a preset voltage when the telephone is on-hook, and a means for disconnecting the bell from the telephone line based on the output of the detection circuit. telephone circuit.