JPH01188196A - Key telephone system - Google Patents

Abstract

PURPOSE:To use a single telephone set as a normal telephone set by respectively inserting a call current detecting circuit to connecting lines in a trunk line trunk side and a single telephone set side. CONSTITUTION:When a call is transferred from a trunk line trunk side to the single telephone set side, a transistor 34 is turned on and off through a control bus 21 by a control circuit 14 and a signal generator 32 for electric bell ringing is connected to the single telephone set. Then, the single telephone set is rung. When the single telephone set executes an off-hook, in case that a C relay is in a short-circuit (make) contact side, a direct current flows out of a direct current power source Vr3l and flows through a release (break) contact side (b) of a B relay 2. Then, the current is passed through a bidirectional photo-diode 8. Accordingly, the off-hook is detected and the control circuit 14 stops the turning-on and off of the C relay 30. Then, the B relay 2 is returned to the short-circuit contact (make) side and after that a relay A is released (breaked). Thus, a terminating call is transferred to the single telephone set.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a button telephone equipment e, and more specifically to a circuit for connecting individual telephones in parallel to a central office line interface circuit of the equipment.

(Prior art) Conventionally, this type of office line interface circuit uses a relay between the trunk circuit and the office line. Insert the -10,000 contact to the trunk side, the other contact to the standalone telephone side, and the middle contact to the central office line side, connect the relay drive line to the power supply, and while the power is turned on, It was configured so that the central office line was connected to the trunk circuit.

(Problems to be Solved by the Invention) The main purpose of the stand-alone telephone in the conventional office line interface circuit described above is to be used as a backup in the event of a failure such as a power failure of the button telephone device. could not be used.

Therefore, it is necessary to install a separate telephone only for backup purposes, which has the drawback of increasing the price of the entire button telephone device.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks and to provide a button telephone device which allows a standalone telephone connected to a central office line interface circuit to be used as a normal telephone.

(Means for solving the problem) The above purpose? In order to achieve this, the button telephone device according to the present invention uses a tip line and a ring line, which are the connection lines of the individual telephones, in parallel with the central office line trunk. Brown 1 and 2 switching devices that connect and open/short-circuit the chip line and ring line of the central office line trunk and the individual telephone connection line in series? The middle contact of the second switch is connected to the standalone telephone side, the shorting contact side is connected to the central office line trunk side, and the open contact side further has a pair of third switches that perform all open/short circuit operations. The middle contact of the switch is connected, the short-circuit side contact of the third switch has a battery, and the open side contact has an independent telephone bell ringing signal generator? The circuits are connected to each other, and all of the call detection circuits are inserted into the connecting lines of the central office line trunk and the individual telephone side, respectively.

(Example) Hereinafter, with reference to all drawings, the preferred embodiment thereof is m f
lJ will be specifically explained.

FIG. 1 is an embodiment of the button telephone device according to the present invention. 1 is a schematic circuit diagram of a portion of a single station line interface circuit.

Office line interface chip (T tap) wire 3 and ring wire (R
ing ) 4 is connected to a central office line (CO), not shown. A single telephone set (SLT) chip line 5 and a single telephone ring line 6 (not shown) are connected to the central office line (
CO) should be connected in parallel. On the central office line trunk side, there is a groove/signal ring detection circuit 7 connected in parallel to the tip line 3 and the ring line 4, and a first circuit inserted in series between the tip line 3 and the ring line 4.
A central line capture A IJ switch which is a switch, a choke 10 for DC termination, and a photodiode 11 for detecting communication current.
The communication path AC transformer 12 is configured to include a series circuit, a communication path AC transformer 12, and a DC blocking capacitor 13 inserted between the windings of the communication path AC transformer 12.

The bidirectional photodiode 8 is connected to a phototransistor 19,
The bidirectional photodiode 11 and the phototransistor 20 are each configured as a photocoupler.

The control circuit 14 is controlled by a central office line trunk control circuit (not shown) via the control bus 21.

Transistor 18 is driven by control circuit 14, and when transistor 18 is in the "on" state.

The b relay winding 16 for the B relay 2 is interlocked, and the B relay at that time
The middle contact of relay 2 is connected to the open contact (break) side.

The middle contact of 131J Ray 2 is connected to the standalone telephone side.

Similarly, when the transistor 17 is in the "on" state, the A+J relay a winding 15 is driven, and the contact of the A relay 1 at this time is connected to the short-circuit contact (make) 1 (11).

The middle contact of the C relay is further connected to the open contact side of the B relay 2, and the short circuit contact (make) of the CIJ relay 0 is connected to the power supply V r 31, and the open contact (break) is connected to the m side of the CIJ relay 0.
B-11 has a signal generator 08 for ringing the bell on a separate telephone.
C2 are connected to each other.

The illustrated contact position of the C relay 30 is the position when the transistor 34 is off and the C relay 30 winding 33 is not driven.

Assume that in the state shown in the figure, there is an incoming call on the central office line, and the central office line trunk responds first and is in a conversation state.

77 That is, when transistor 17 is on, A relay 1 is shorted (make 3L), and when transistor 18 is on, B relay 2 is on the open (break) contact side, and C relay 30 is shorted (make) contact. It is assumed that it is on the m side.

At this time, when transferring a call from the central office line trunk side to the standalone telephone @ '131u, control bus 21? Control circuit 1 through
4, the transistor 34 is turned on and off, the bell ringing signal generator 32 is connected to the individual telephone, and the individual telephone is made to ring. When a single phone goes off-hook, C relay 3
When o is on the short circuit (make) contact side, DC power supply Vr31
A direct current flows out and passes through the bidirectional photodiode 8 on the open (break) contact side of the B+J relay 2. This detects off-hook. - Once off-hook is detected, the control circuit 14 completely stops the on/off control of the C relay 30, and returns the 331J relay 2 to the short-circuit contact (make) side.

After that, relay Ai is opened (broken).

The above operation means that the incoming call is transferred to the individual telephone set.

(Effects of the Invention) As explained above, according to the present invention, an individual telephone connected in parallel (branch) to the central office line interface circuit of a button telephone device is connected to a central office line connected in parallel (branch) of the individual telephone. This has the advantage that only calls from one office line can be transferred from a single office line trunk.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of a key telephone device according to the present invention, and is a schematic circuit diagram of a portion of a single station line interface circuit. 1... A IJ relay first switching device for station line acquisition) 2.
...B relay (second switch) 3...Tip line 4...Ring line 5...Single telephone (SLT) tip line 6...Single telephone (S L T ) IJ ring line 7... Incoming ring detection circuit 8... Bidirectional photodiode (photocoupler in pair with 20) 9... Station arriving signal line 10... DC termination choke 11... Photodiode for detecting communication current (photocoupler in pair with 19) 12... Multi-current transformer for communication path 13... Capacitor for direct current blocking 14... Control circuit 15... A winding for A relay 16... B relay winding 17, 18, 34...transistor 19...phototransistor 20...phototransistor 21...control bus 30...C relay 31...DC power supply ■r 32...・Signal generator for single telephone bell ringer (0SC) 33... C winding for C relay patent applicant NEC Corporation

Claims (1)

[Claims] Connect the tip line and ring line, which are connection lines for the individual telephone, in parallel to the central office line trunk, and open and connect the chip line and ring line in series to the respective tip line and ring line of the central office line trunk and the individual telephone connecting line.
First and second switching devices for short circuiting are inserted, the middle contact of the second switching device is connected to the single telephone side, the shorting contact side is connected to the central office trunk side, and the open contact side is connected to the central telephone side. further connects the middle contacts of a third switching device that performs opening and shorting, and connects a battery to the shorting side contact of the third switching device.
A button telephone device characterized in that an individual telephone bell ringing signal generator is connected to each open side contact, and a speech current detection circuit is inserted in each of the connecting lines on the central office line trunk side and the individual telephone side. .