JP2917028B2 - Private branch exchange - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention automatically captures and transmits another station line by using a multi-frequency selection signal (hereinafter referred to as DTMF) from a station line, and transmits the signal to the station line. The present invention relates to a private branch exchange (hereinafter, referred to as a PBX) having an office line transfer function enabling office line communication.

(Prior Art) FIG. 5 shows a configuration of a conventional PBX having a local line transfer function. In FIG. 5, reference numerals 1 and 2 denote a line interface unit for acquiring a line, receiving a bell signal from the line, impedance matching, and the like.
8 and transformers 9 and 10. Reference numerals 3 and 4 denote extension interface units capable of accommodating internal telephones, reference numerals 5 and 6 denote extension telephones, reference numeral 11 denotes an office line to an extension, or an office line to a 2-wire to 4-wire conversion unit, or a cross-point switch unit for connecting extensions to each other. , 12 and 13 are two-wire to four-wire converters, and amplifiers 14 and 1
5, 16, 17, etc. 18 and 19 are switches for connecting the respective 2-wire to 4-wire converters 12 and 13, and 21 is a DTMF from the office line.
A DTMF receiver for detecting a signal, 23 is a recording message transmitting unit (hereinafter referred to as OGM) for transmitting a recording message to a local line, and 27 is a control unit for controlling each unit.

Next, the operation of the conventional office line transfer function will be described with reference to FIGS. 6 and 7 are conventional time charts.

First, a case where a call is transmitted from the station line a to the station line n will be described. When there is an incoming call on the office line a, the incoming call is detected by the bell detection circuit 7 of the office line interface unit 1, the cross point is turned on by the cross point switch unit 11, and the office line interface unit 1 and the 2-line-4 line The conversion unit 12 is connected. Thereafter, the OGM 23 sends out a recording message on the line a (via the route of 23-15-11-1), and the DTMF receiver 21 performs DTMF reception.
Monitors the MF signal.

Next, when a DTMF signal for outside line acquisition is sent from the office line a
The DTMF receiver 21 is detected (in the route of 1-11-14-29-21), the recording message from the OGM 23 stops, the switches 18 and 19 are turned on, and the crosspoint switch unit 1 is turned on.
The predetermined cross point 1 is turned on, the office line interface unit 2 corresponding to the office line n and the 2-wire to 4-wire conversion unit 13 are connected, and a path between the office line a and the office line n is established. After that, office line a
When the DTMF code of the dial number is transmitted, the signal is transmitted from the office line n (1-11-14-19-19-17-11).
-2 route). FIG. 6 shows a time chart of the above operation.

Next, when the office line a and the office line n are connected as described above and are in a talking state, when a DTMF signal is sent from the office line a, the DTMF signal is sent directly to the office line n (1- 11-14-19-
17-11-2). FIG. 7 shows a time chart of the above operation.

(Problems to be Solved by the Invention) However, in the above-described conventional configuration, when a DTMF signal transmitted from an office line is transmitted to another office line via a 2-wire to 4-wire conversion unit, the line distance is long. As a result, the level of the DTMF signal becomes smaller, and there is a problem that the line side does not accept it as a dial signal.

The present invention solves such a conventional problem, and can transmit a DTMF signal whose level does not decrease to a local line, and can prevent a signal from being sneak from another local line which causes a malfunction. It is intended to provide a PBX.

(Means for Solving the Problems) In order to achieve the above object, a PBX of the present invention comprises a central office interface unit connectable to a central office, and two 2-wire-4
A line converter, the office line interface, and the two wires
A cross point for connecting the four-wire converter, a first switch for connecting the two two-wire to four-wire converters to each other,
Message sending unit (OG
M) and D which receives the multi-frequency selection signal (DTMF) from the office line
A TMF receiver, a DTMF generator for transmitting a DTMF signal to the office line, a second switch for connecting the DTMF generator and the 2-wire to 4-wire conversion unit, and a control unit for controlling each unit, the control unit In the office line transfer state, the first switch is turned on to connect an audio path between two office lines, and in the office line transfer state, when the DTMF receiver detects a DTMF signal, the first switch is turned on. Turn off, then
When the DTMF signal is continuously detected, the second switch is turned on, and the DTMF signal is received by the DTMF receiver.
In this configuration, the same signal as the DTMF signal is output from the DTMF generator.

(Operation) Therefore, according to the present invention, by outputting the same signal as the DTMF signal received by the DTMF receiver from the DTMF generator, it is possible to reduce the transmission level of the DTMF signal even when the line distance becomes longer. Can be prevented, and
When the DTMF signal is detected by the DTMF receiver during a voice call, it is checked whether the DTMF signal is detected continuously.If the DTMF signal is detected continuously, the signal is not transmitted from another line. By outputting the DTMF signal received by the DTMF generator from the DTMF generator, it is possible to prevent a signal from being transmitted from another station line.

(Embodiment) FIG. 1 shows a configuration of a PBX having a local line transfer function according to an embodiment of the present invention. In FIG. 1, the fifth
The same numbers as in the conventional example in the figure have the same functions. 2 to 4 are time charts of the present embodiment.

In FIG. 1, reference numerals 1 and 2 denote a line interface unit for acquiring a line, receiving a bell signal from the line, impedance matching, and the like. The bell detection circuits 7 and 8 and the transformers 9 and 1 are provided.
Has zero. Reference numerals 3 and 4 denote extension interface units capable of accommodating extension telephones, reference numerals 5 and 6 denote extension telephones, reference numeral 11 denotes a cross-point switch unit, reference numerals 12 and 13 denote 2-wire to 4-wire conversion units, and amplifiers 14, 15, 16, and 17. Have. 18 and 19 are 2-wire-4
A switch for connecting the line converter, 20 is a 2-wire to 4-wire converter 13
Integrating circuit for averaging the audio level from, 21 is a DTMF receiver, 23 is OGM, 24 is a comparator that compares the reference voltage with the level of the integrating circuit 20, and 26 is the same as the voltage level clipped at the output of the amplifier 16. Reference voltage, 27 is a control unit, 28 is a switch that connects the DTMF generator and the 2-wire to 4-wire conversion unit, and 36 is a switch.
DTMF generator that generates DTMF signals.

Next, the operation of the local line transfer function in the present embodiment will be described with reference to FIGS.

In FIG. 1, a case where a call is transmitted from the station line a to the station line n will be described first. When there is an incoming call on the office line a, an incoming call is detected by the bell detection circuit 7 of the office line interface unit 1, a predetermined cross point of the cross point switch unit 11 is turned on, and the office line interface 1 and the 2-wire to 4-wire conversion unit are turned on. Connect 12 Thereafter, the OGM 23 sends a recording message to the station line a (via the route 23-15-11-1), and the DTMF receiver 21 monitors the DTMF signal.

Next, when a DTMF signal for capturing an outside line is transmitted from the station line a, the DTMF signal is detected by the DTMF receiver 21 (by the route of 1-11-14-29-1), and the recording message from the OGM 23 is stopped. 19 turns on, and the line interface units 2 and 2
The line-to-line converter 13 is connected, and a path between the office line a and the office line n is created. Thereafter, when a DTMF signal of the office line dial number is sent from the office line a (in the route of 1-11-14-21), the DTMF signal is output.
The detection signal 30 transmitted to the MF receiver 21 has a high potential (High). Then, the wraparound from the local line n (2-11-16-18)
The switch 18 is turned off in order to determine that the signal is not a signal according to (−15−14−21). If the output (detection signal) 30 of the DTMF receiver 21 is still high, it is regarded as normal, the switch 28 is turned on, and the same signal as the received DTMF signal is transmitted from the DTMF generator 36 to the local line n. Since then
The office line dial number is transmitted by the same operation. FIG. 2 shows a time chart of the above operation.

Next, when the office line a and the office line n are connected as described above and a call is in progress, when a DTMF signal is transmitted from the office line a, the DTMF signal from the office line a is transmitted to the DTMF receiver 21. Is detected. Then, in order to distinguish between the audio signal and the DTMF signal,
Look at the output of DTMF receiver 21 after 28 ms, and if it is high potential,
It is determined that the signal is a DTMF signal, the switch 18 is turned off, and then a check is made to see if the signal is due to a wraparound tone (in the route of the local line n-2-11-16-18-18-15-14-21). If not, the switch 28 is turned on, and the same DTMF signal as the received signal is transmitted from the DTMF generator 36 to the station line n. FIG. 3 shows a time chart of the above operation.

More specifically, the wraparound signal from the office line n will be described. For example, when a voice call is being made between the office line a and the office line n, the signal is provided in each of the 2-wire to 4-wire conversion units 12 and 13. The audio signals are bidirectionally amplified by the amplifiers 14 and 15 and the amplifiers 16 and 17 that are provided. DTMF receiver 21 is 2-wire to 4-wire converter 1
2 and 13 are always connected, and when a DTMF signal is transmitted from the station line a, the DTMF signal amplified by the amplifier 14 can be detected. Since the forward and return signals cannot be completely separated, when the signal from the local line a can be received, the signal from the local line n goes through the amplifier 15 to the input side of the amplifier 14 and the DTMF receiver 21 May be entered.

Next, the check of the sneak signal by the control unit 27 will be described with reference to FIG.
As soon as the MF receiver 21 detects the DTMF signal, the 2-wire-4
Turn off the switch 18 between the line conversion units 12 and 13, and then
It is checked whether or not the F signal is continuously detected.If the F signal is detected, the signal is not a wraparound signal.Therefore, the switch 28 provided on the output side of the DTMF generator 36 is turned on, and the DTMF generator 36 The same as the received signal to office line n
The DTMF signal is sent.

The integration circuit 20 and the comparator 24 are provided when a strong voice from the local line n (a level at which the waveform is clipped by the outputs of the amplifiers 15 and 16) is input and the signal is wrapped around (local line n-2-11-). 16
This is to prevent the DTMF receiver 21 from operating on the route (−18−15−14−21) and the above-mentioned switch 18 being turned on / off to interrupt the call. When a sound higher than the reference voltage 26 (the maximum voltage that does not clip at the outputs of the amplifiers 15 and 16) comes in, the output of the comparator 24 is set to a high potential so that it is not regarded as receiving a DTMF signal. FIG. 4 shows a time chart of the operation in this case.

(Effect of the Invention) As described above, according to the present invention, the input DT
The MF signal can be received once, and the signal can be transmitted at a higher level with the DTMF generator, preventing the dial signal from being rejected on the local line due to the level drop on long-distance lines. And when you are in a voice call
If the DTMF signal detected by the DTMF receiver is not sneak from another station line, the DTMF signal received by the DTMF receiver can be output from the DTMF generator. it can.

[Brief description of the drawings]

FIG. 1 is a block diagram of a PBX having an office line transfer function according to an embodiment of the present invention, FIGS. 2 to 4 are operation time charts of the embodiment, and FIG. 5 has a conventional office line transfer function.
FIGS. 6 and 7 are diagrams showing the operation of the conventional PBX. 1,2: office line interface, 3,4 ... extension interface, 5,6 ... extension telephone, 7,8 ... bell detection circuit, 9,10 ... transformer, 11 ... cross point switch , 12, 13, ... 2-wire to 4-wire converter, 14, 15, 16, 17 ... amplifier, 18, 19, 28 ... switch, 20 ... integration circuit, 21 ... DT
MF receiver, 23 …… Recorded message sending unit (OGM), 24
... Comparator, 26 ... Reference voltage, 27 ... Control unit, 36 ... DT
MF generator.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04Q 3/58 H04M 1/00 H04M 3/42-3/58 H04Q 1/45 H04Q 3/42

Claims (1)

(57) [Claims] A central station interface connectable to a central office, two 2-wire to 4-wire converters, a cross point connecting the central office interface to the 2-wire to 4-wire converter, A first switch for interconnecting the two 2-wire to 4-wire converters, a message sending unit (OGM) for sending a recording message to the office line, and receiving a multi-frequency selection signal (DTMF) from the office line A DTMF receiver that transmits a DTMF signal to a local line, a second switch that connects the DTMF generator and the 2-wire to 4-wire conversion unit, and a control unit that controls each unit. In the office line transfer state, the first switch is turned on to connect the audio path between the two office lines, and in the office line transfer state, the first switch is turned on when the DTMF receiver detects a DTMF signal. Off, and then the DTMF signal is While turning on the second switch when it is detected, and private automatic branch exchange, characterized in that the DTMF signal identical to the signal was configured to output from the DTMF generator received by the DTMF receiver.