JPH0323747Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Technical field of invention] The present invention relates to a central office line circuit for telephone equipment.

[Technical background of the invention]

Generally, a central office line circuit of a telephone device disconnects the line and detects incoming calls, and a conventional central office line circuit is shown surrounded by a chain line in FIG. 1.

That is, the office line circuit 10 is an incoming call circuit that detects an incoming call by detecting the line disconnection contact 1 inserted into one of the telephone lines L ₁ and _{L 2} and a ringing signal from the office line circuit 10. 2, the telephone lines L ₁ and L ₂ are connected to the terminals T ₁ and T ₂ of the office line circuit, and the telephone line switching circuit 4 that switches the connection with the extension telephone 3 is connected to the terminals T ₃ and T ₄ . is connected.

The line connection contact 1 is connected to a series circuit of a resistor 51 and a capacitor 52 to prevent damage to the contact due to spark current (discharge current that jumps between contacts) that occurs when the telephone line is opened (disconnected) due to end of call, etc. A contact protection circuit 5 is provided. This contact protection circuit 5 is absolutely necessary because the load on the contacts is an inductance load caused by relays of telephones and exchanges.

[Problems with background technology]

By the way, the contact protection circuit 5 needs to have a high withstand voltage, both because it absorbs high voltage and because it is connected in a straight line to the line and is directly affected by ring signals and line noise from other devices. However, a relatively large one with an expensive shape is used. Since the contact protection circuit 5 needs to be provided for each line, this poses a large burden in terms of cost and implementation, especially in devices that accommodate a large number of lines.

[Purpose of invention]

This invention was made for the purpose of eliminating the above-mentioned problems.

[Summary of the idea]

This invention focuses on the fact that the incoming circuit includes a circuit that includes a DC blocking capacitor, and is characterized in that the contact protection circuit is formed using the capacitor of this incoming circuit. In other words, in this idea,
A movable contact piece is connected to one own side of a pair of telephone lines, a first fixed contact and a second fixed contact are connected to the central office side of the one telephone line and the other telephone line, respectively, and the movable contact piece has a switching contact that is connected to the second fixed contact in the standby state and connected to the first fixed contact in the operating state, and a resistance is connected between the movable contact piece of the switching contact and the first fixed contact. By connecting an incoming circuit that includes a series circuit of a capacitor and a capacitor, the capacitor of the incoming circuit is used as a contact protection circuit, making it possible to protect the contacts without providing a special contact protection circuit.

[Example of idea]

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 shows an embodiment of the station line circuit according to the present invention, and the same reference numerals are used for parts that perform the same functions as in FIG. 1.

In Figure 2, out of telephone lines L ₁ and L ₂ , the line
L ₁ is directly connected to the communication path switching circuit 4 via the terminal T ₃ of the office line circuit 10, and line L ₂ is connected to the relay contact circuit 6 consisting of 1 circuit and 3 contacts, and the terminal of the office line circuit 10.
It is connected to the communication path switching circuit 4 via _T4 .

Note that the contact piece 6a of the relay contact circuit 6 is closed when the handset of the extension telephone 3 is on-hook.
b, and is switched to contact 6c by off-hooking the handset of extension telephone 3.

Now, when a calling signal is applied to the terminals T ₁ and T ₂ of the office line circuit 10, the calling signal is applied to the terminal T ₁ , line L ₁ ,
Contact 6b, contact piece 6a, resistor 21, DC blocking capacitor 22, line L ₂ , terminal T ₂ and flow, resistor 21
A voltage of a predetermined magnitude is extracted from the incoming call detection circuit 23, and this voltage is detected by the incoming call detection circuit 23, which generates an incoming call signal RS based on the above detection.

FIG. 3 shows a detailed circuit example of this incoming call circuit. In this detailed circuit example, a diode 24 corresponds to the incoming call detection circuit 23.
and a photocoupler 25 are used. A ringing signal applied from the telephone line L ₁ through the contacts 6b and 6a of the relay contact circuit 6 (see Fig. 2) is transmitted through the resistors 26, 21, and the DC blocking capacitor 2.
2 to the line L ₂ , and a predetermined voltage is generated on both sides of the resistor 21 . This voltage is applied to the photocoupler circuit 25 via the rectifying diode 24. As a result, the light emitting diode 25a of the photocoupler 25 emits light, and an incoming signal RS is generated from the emitter of the phototransistor 25b.

The incoming call signal RS is applied to the extension telephone 3 in a circuit not shown, and the extension telephone 3 makes a speaker or the like ring based on the incoming call signal RS to indicate an incoming call.

When the extension telephone 3 takes off the handset and responds to the incoming call display, the contact 6a (see Fig. 2) of the relay contact circuit 6 is switched, the contact 6a is connected to the contact 6c, and the circuit _L2 is connected. You can make phone calls using this function.

Next, when ending the call, when the handset of the extension telephone 3 is turned on, the contact piece 6a of the relay contact circuit 6
is again connected to contact 6b.

In this way, the contact piece 6a of the relay contact circuit 6 of the office line circuit 10 is switched from the contact 6b to the contact 6c and from the contact 6c to the contact 6b in response to the off-hook and on-hook of the extension telephone 3, but in this case, the incoming call circuit A circuit consisting of a resistor 21, a resistor 2b, and a capacitor 22 operates as a protection circuit for the contacts 6b and 6c of the relay contact circuit 6.

That is, between the contact piece 6a and the contact point 6b, and between the contact piece 6a and the contact point 6c, the generation of high voltage due to a transient phenomenon at the time of opening or closing is absorbed by the capacitor 22 to prevent arc discharge.

Further, when arc discharge occurs immediately after opening, the current is shunted to the capacitor 22 to prevent the development of steady arc discharge, and also to prevent the generation of noise due to arc discharge.

[Effect of idea]

As explained above, according to the present invention, there is no need to specifically provide a contact protection circuit for the relay for connecting the office line, the load on the mounting side is reduced, and an increase in cost can be suppressed. The effect on telephone equipment having a central office line is significant.

Furthermore, the incoming call circuit is short-circuited during a call, thereby preventing malfunctions.

[Brief explanation of drawings]

Figure 1 shows a block diagram of a conventional station line circuit.
FIG. 2 is a block diagram showing an embodiment of the central office line circuit according to the present invention, and FIG. 3 is a block diagram of a receiving circuit. 1... Line disconnection contact, 2... Incoming circuit, 3...
... Extension telephone, 4 ... Call path switching circuit, 5 ... Contact protection circuit, 6 ... Relay contact circuit, 21 ... Resistor, 22 ... Capacitor, 23 ... Incoming call detection circuit, 24 ... Diode, 25 ... ...Photocoupler, 26...Resistor, 51...Resistor, 52...Capacitor, L ₁ ...Telephone line, L ₂ ...Telephone line, T ₁
... terminal, T ₂ ... terminal, T ₃ ... terminal, T ₄ ... terminal.

Claims (1)

[Claim for Utility Model Registration] In a station line circuit equipped with a receiving circuit having a series circuit of a resistor and a capacitor between input and output terminals, a movable contact piece is connected to one self side of a pair of telephone lines, and A first fixed contact and a second fixed contact are connected to the office side of one telephone line and the other telephone line, respectively, and the movable contact piece is connected to the second fixed contact in the standby state and in the operating state. a switching contact connected to the first fixed contact;
A station line circuit characterized in that the incoming circuit is connected between the movable contact piece of the switching contact and the first fixed contact.