JPH01290353A - Ring trip circuit - Google Patents

Abstract

PURPOSE:To make the ring trip circuit small in size in a digital subscriber circuit of a time division exchange by connecting a low pass filter across a resistor for ringer transmission and connecting a ringer detection circuit to the output in parallel. CONSTITUTION:A cal signal is sent from a call signal generator 3 to a subscriber telephone set 2 through a call signal transmission circuit and when the subscriber telephone set 2 hooks off, a voltage across a resistor 7 for ringer transmission passes through a low pass filter 8 and is given to a ringer detection circuit 9. When the voltage exceeds a threshold value depending on a Zener diode of the ringer detection circuit 9, a current flows to a photo transistor and a ring trip signal is sent to the network side. Thus, the call signal transmission circuit is restored and the subscriber telephone set 2 is connected to the subscriber circuit 1.

Description

[Detailed Description of the Invention] [Summary] The purpose of this invention is to reduce the size of the ring trip circuit in the digital subscriber circuit of a time division exchange without increasing the number of parts. A low-pass filter consisting of a resistor and a capacitor is connected to both ends of the device, and a ringer detection circuit consisting of a series circuit of a Zener diode and a phototransistor is connected in parallel to the output side of the low-pass filter.

[Industrial application field]

The present invention relates to ring trip circuits in digital subscriber circuits.

The subscriber circuit of a digital exchange has a ring trip circuit for detecting a response when a calling signal is sent out, and is not impressed by the alternating current (approximately 16 Hz to 2511 Hz) current of the calling signal, but rather detects the direct current voltage at the time of answering. It has a ring trip function to detect.

[Conventional technology]

Figures 3 and 4 show examples of circuit configurations of conventional ring trip circuits.
As shown in the figure. FIG. 3 shows an example of a circuit using a large capacity capacitor, and FIG. 4 shows an example of a circuit designed to be miniaturized.

In Fig. 3, 1 is a subscriber circuit consisting of a power supply circuit and others, 2 is a subscriber telephone, 3 is a ring signal generator, and 4 is a ring trip circuit. It consists of a resistor R, a Zener diode ZD, and a phototransistor circle 1. The alternating current signal CR from the ringing signal generator 3 is sent to the subscriber's telephone 2 by turning on and off the ringing signal relay contact r6. The calling signal sending circuit is -48V -CR-(S) -C-RO-'r
1-(R)-Telephone-(T)-rl-R1-A calling signal is sent through the earth path. Capacitor C and resistor RO constitute a filter circuit, and since resistor RO is determined to be about IKΩ from the relationship with the line resistance, capacitor C has a large capacity of 50 to 100 μF. Therefore, large capacity capacitors such as polarized capacitors or electrolytic capacitors must be used. When the subscriber telephone a2 is turned off and turned on, a DC voltage of -48V is detected through a path passing through the resistor R of the ring trip circuit 4, the Zener diode ZD, and the phototransistor PH, and the phototransistor PH is detected.
operates to send an "O" signal to the scan signal terminal SCN, activate the network circuit as a ring trip signal, and return the ringing signal sending relay contact rl to connect the subscriber telephone 2 to the subscriber circuit I. The resistance R is 10 KΩ,
When the Zener diode ZD exceeds a certain current, the current direction is reversed and the phototransistor PR is activated.

Next, in the conventional example shown in Fig. 4, which is suitable for miniaturization, 1°2.3
is the same device as in Fig. 3, and 5 is a ring trip circuit connected to both ends of the ringer sending resistor RO, and the current detecting resistor R
2. R3, differential amplifier AP, resistor R6 and capacitor C
It consists of a filter consisting of I, a comparator CP, and a phototransistor PH. Relay contact rt for calling signal sending
! is inserted into the sending circuit of the calling signal generator 3 in addition to the tip and ring wires.

This is because when the ring signal sending relay contact rl is restored, the ring signal flows to the ring trip circuit 5 and the detection resistor R3 and R
4 becomes a load on the ringing signal generator 3. For example, if there is one ringing signal generator 3 in 1000 subscriber lines, the parallel resistance of R2 and R3 is 1/1000.
This is to prevent overload from becoming a load resistance. Therefore, the load on the contact rl of the calling signal sending relay is correspondingly heavy.

As for the circuit operation, the alternating current signal CR from the calling signal generator 3 is sent to the subscriber telephone 2 by turning on and off the calling signal sending relay contact rff. The calling signal sending circuit is -48V.
-CR-(S) -rll -RO-rl -(R)~
A ringing signal is sent out via the telephone -(T)-rll-Ri-earth route. When subscriber telephone 2 goes off-hook, current flows through current detection resistors R2 and R3, a voltage corresponding to the difference between the two currents is detected by differential amplifier AP, and R
6 and 01 and is sent to the comparator CP. The comparator CP compares this voltage with the threshold value 7, and if it exceeds the threshold value, activates the phototransistor Pl+, sends the ring trip signal SCN to the network side, and activates the ring trip signal SCN to the ring signal relay. Restore the contact rf,
The subscriber telephone 2 is extended to the subscriber circuit 1 and subsequent circuit operations are performed.

In the above circuit, the detection resistors R2 and R3 are each IM
The resistors R4 and R5 have a large resistance value of about 100Ω.

[Problem to be solved by the invention]

Therefore, an object of the present invention is to provide a ring trip circuit that does not use large capacitors or resistors unlike conventional ring trip circuits, and does not overload the ringing signal generator.

For this reason, the circuit configuration is such that the load on the relay contact for sending out the calling signal is as light as possible, and large components such as electrolytic capacitors are not used.

[Means to solve the problem]

FIG. 1 shows a basic configuration diagram of the present invention. In the figure, 1 is a subscriber circuit consisting of a power supply circuit and others, 2 is a subscriber telephone, and 3
is a ringing signal generator; 6 is a ring trip circuit; It consists of Note that a conventional calling signal sending relay contact for disconnecting the calling signal sending route from the calling signal generator 3 except during calling is not provided.

[Effect]

A ringing signal is sent from the ringing signal generator 3 to the subscriber telephone 2 by the ringing signal sending circuit, and when the subscriber telephone 2 goes off-hook, the voltage across the ringer sending resistor 7 passes through the low-pass filter 8, and the ringer is detected. applied to circuit 9. When this voltage exceeds a threshold value determined by the Zener diode of the ring detection circuit 9, current flows through the phototransistor and sends a ring trip signal to the network side. As a result, the calling signal sending circuit is restored and the subscriber telephone 2 is connected to the subscriber circuit 1.

〔Example〕

FIG. 2 shows a circuit configuration diagram of an embodiment of the present invention.

In the figure, the subscriber circuit 1 consists of a power supply circuit, a monitoring circuit, a 2-wire/4-wire conversion circuit, a codec circuit, etc., and is a circuit that connects the subscriber telephone 2 to the network side. 1 (illz~25
This is a circuit that sends out an Itz AC signal, and is provided in common to subscriber circuits. The ringer sending resistor 7 constituting the ring trip circuit 6 is a resistor RO of IKΩ, and is connected to the ringing signal sending route by the ringing signal sending relay contact rl, and detects the DC superimposed current caused by the off-hook of the subscriber telephone 2. sends a voltage across the resistor RO. The low-pass filter 8 is composed of a resistor R2 of IOKΩ and a capacitor C2 of about 5 μF, and serves to smooth the voltage across the ringer sending resistor RO. Ringer detection circuit 9
are Zener diode ZD and phototransistor I'l+
and a resistor R7, and when the Zener diode ZD exceeds the threshold current, the rectifying direction is reversed, ignites the phototransistor PI, and operates the contact of the phototransistor PH.Therefore, the ring trip signal SCN is set to "H".
The signal is converted from "L" to "L" and the scan signal is sent to the network side. This allows the relay contact rl for sending out the calling signal to
is restored, subscriber telephone 2 is connected to subscriber circuit 1,
You can talk to the other party's phone. In the above circuit,
Since the low-pass filter 8 and the rectifier side of the ringer detection circuit 9 are insulated from the earth, they do not place a load on the ringing signal generator 3 when no ringing signal is being sent out, and the ringing signal can be sent out as before. There is no need to add a relay contact rl to disconnect the calling signal sending route. Furthermore, the CR product constituting the low-pass filter 8 is approximately a constant value (approximately 10 On+s).
is required, and in order to reduce the capacitance of C2, R2 should be chosen large. On the other hand, R2 limits the current flowing to the photocoupler I'l+, so the upper limit of R2 is approximately IOK.
It will be about Ω. At this time, the capacitance of C2 becomes approximately 5 to 10 .mu.F, and the capacitance of the capacitor can be reduced.

〔Effect of the invention〕

The ring trip circuit of the present invention eliminates the need to overcurrent the load of the call signal sending relay contact, eliminates the need to use large capacity capacitors and high resistance, and reduces the number of components without increasing the number of components. can be made possible.

[Brief explanation of the drawing]

Figure 1 shows the principle configuration of the present invention, Figure 2 shows the circuit configuration of an embodiment of the invention, Figure 3 shows the circuit configuration of a conventional example, and Figure 4 shows the circuit configuration of another conventional example. . In the figure, l is a subscriber circuit, 2 is a subscriber telephone, 3 is a ringing signal generator, 4, 5.6 is a ring trip circuit, and 7 is a subscriber circuit.
8 is a low-pass filter, and 9 is a ringer detection circuit.

Claims (1)

[Claims] In a ring trip circuit in a digital subscriber circuit of a time division exchange, a low pass filter (8) consisting of a resistor and a capacitor is connected to both ends of a ringer sending resistor (7), and the low pass filter (8) is connected to both ends of a ringer sending resistor (7). 8) A ringer detection circuit consisting of a series circuit of a Zener diode and a phototransistor is installed on the output side (
A ring trip circuit characterized by connecting 9) in parallel.