JPH0370958B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a subscriber status detection circuit in an automatic exchange.

(Prior Art) Conventionally, in an automatic switching system, the status of a subscriber's call origination, disconnection, dial pulse reception, and response has been detected by a subscriber circuit and its status detection circuit.

The configuration will be explained below using figures.

Figure 2 shows an example of the configuration of a conventional subscriber status detection circuit, where 1 is a subscriber line connected to a subscriber (telephone) TEL, BF is a call current supply circuit connected to subscriber line 1, and R1 is a voltage. A detection resistor, R2 is a resistor, 2 is a DC power supply with voltage E (for example, +24V), r
0 is a contact that opens and closes in response to sending a calling signal, which will be described later. DO is a diode that turns on when the polarity of the calling signal is reversed. IR is a contact that superimposes an AC oscillation voltage on the voltage E of the DC power supply 3, and generates this as a calling signal. 4 is a control signal CTL generator for operating and restoring the calling signal sending relay;
Q0 is a transistor that responds to the control signal output through resistor R3, RL is a call sending relay connected via power supply 5 between the collector and emitter of transistor Q0, CMP is a comparator, and R4 is a transistor that connects one end of resistor R1 to the comparator CMP. Resistor connected between one input terminal, 6 is comparator
Reference power supply that inputs reference voltage V _REF to the other input terminal of CMP, r1 is resistor R4 and comparator
Resistor R5 with one end grounded at the midpoint of connection with CMP
Alternatively, it is a contact connected to one end of the capacitor C1 which together with the resistor R4 forms a low-pass filter, and this contact, together with the contact r0, responds to the relay RL.

Next, the operation will be explained.

Now, if we are not in the state where a ringing signal is being sent, but are detecting whether the subscriber is calling, disconnecting, or receiving a dial pulse, the ringing signal sending relay RL is inactive, and the resistance of the call current supply circuit BF is The voltage change occurring in R1 is compared to the reference voltage V _REF by a comparator.
CMP was used to identify subscriber calls, disconnections, and receipt of dial pulses.

On the other hand, when the ring signal generation circuit IR is operated and a ring signal is sent to the subscriber, the control signal CTL output from the control signal generator 4 turns on the transistor Q0, and the ring signal sending relay
RL operates and sends a calling signal to the subscriber line 1 through its contact r0, and at the same time sends a ringing signal to the subscriber line 1 through its contact r0.
By connecting the capacitor C1 to the input circuit of the comparator CMP, out of the calling signal voltage (including AC and DC components) obtained at the voltage detection resistor R1,
The AC component (20 Hz) is removed by a low-pass filter consisting of a capacitor C1 and a resistor R4, only the DC component is separated, and a response signal corresponding to the DC component is detected.
In this way, signals corresponding to each subscriber's status at the time of calling, disconnecting, receiving dial pulses, and calling can be obtained as the comparator CMP output.

(Problem to be Solved by the Invention) In the circuit with the above configuration, when a subscriber makes a call or receives a dial pulse, a DC current flows through the subscriber line 1, and the resistor R1 responds to this current. On the other hand, when a subscriber responds while a calling signal is being sent, a direct current flows through the subscriber line 1, and a voltage is obtained across the resistor R1.

However, although most of the calling signal, which is an alternating current signal, is discharged through the capacitor C1, a part of the calling signal voltage (for example, ±75Vp-p) remains undischarged, and this results in calls being made, disconnected, and dialed. At the time of pulse reception and at the time of sending out a calling signal, the resistor R1 is
These two different voltages, i.e. call origination/disconnection or dialing pulse on/off and response/non-response, are compared with one reference voltage V _REF by comparator CMP. Also, the comparator
There was a problem that the detection level margin of CMP was also insufficient.

The present invention provides a subscriber status detection circuit for an automatic switching system that is capable of detecting the two different voltages in a comparator CMP based on one set reference voltage even though the voltages generated in the resistor R1 are different. The purpose is to

(Means for Solving the Problems) The present invention has been made to achieve the above object, and in a subscriber state detection circuit of an automatic exchange, a voltage detection resistor is provided in the subscriber circuit, and the voltage detection A capacitor is connected to the resistor via a switch means that is closed when a ringing signal is generated, and a comparator compares the voltage detected by the voltage detection resistor with a set reference voltage, thereby determining whether or not the subscriber is making a call. The presence or absence of a response to disconnection, dial pulse reception, and calling is detected respectively, and by connecting a resistor in the circuit connecting the voltage detection circuit and the comparator, the voltage detection resistor is turned on and off by the switching means. The structure is such that the difference in voltage obtained between the two is adjusted.

(Function) According to the present invention, when a calling signal is generated, by switching the switch means, it is possible to simultaneously add a resistor for compensating the low-pass filter and the voltage detection resistor to the input circuit of the comparator. , even though there is a difference in the voltage level at the voltage detection resistor when receiving a dial pulse and when responding while sending a ringing signal, it is easy to
A set reference voltage serving as a reference can be set as the input of the comparator, and the subscriber status can be detected with high precision and under the same conditions.

(Embodiment) FIG. 1 is a circuit diagram showing an embodiment of the present invention, in which a transistor Q1 as a switching means is connected to a midpoint between a control signal generator 4 and a resistor R3 via a resistor R6. Base is connected. The emitter of this transistor Q1 is connected. On the other hand, the voltage detection resistor R1 and the communication current supply circuit
A series resistor R8 for a low-pass filter is connected between the connection midpoint with BF and the comparator CMP via a resistor R7. Also, resistors R7 and R8
A resistor R9 is connected between the midpoint of the connection between the resistor R8 and the collector of the transistor Q1, and a capacitor C2 constituting a low-pass filter is connected between the midpoint of the connection between the resistor R8 and the comparator CMP and the collector of the transistor Q1. It is connected.

Note that other components that are the same as those shown in FIG. 2 are given the same reference numerals, and redundant explanation thereof will be omitted.

Next, the operation will be explained.

If we are currently detecting a subscriber's call origination, disconnection, or dial pulse reception rather than the sending of a ringing signal, the change in the current flowing through the current supply circuit BF is determined by the voltage detection resistor R1. converted to voltage. Also, at this time, the call signal sending relay
Since RL is inactive and transistor Q1 is off, the voltage obtained across voltage detection resistor R1 passes through resistors R7 and R8 to the comparator.
CMP is input, and when this voltage exceeds the reference voltage V _REF , the comparator CMP outputs a signal to detect a loop in the subscriber line. In this case,
The input impedance of the comparator CMP is high, and the voltage detection resistor is The voltage generated at R1 is input to the comparator CMP without changing.

On the other hand, when the calling signal is being sent, both transistors Q0 and Q1 are turned on, and the calling signal sending relay RL is operated, so that the contact r0
A calling signal is sent to the subscriber. Also, at this time, the voltage appearing on the voltage detection resistor R1 is the resistor R
7. The voltage is divided by R9 to the ratio of R9/(R7+R9), and the AC component (20Hz) included in the detected voltage is removed by a low-pass filter circuit consisting of resistor R8 and capacitor C2. and input to comparator CMP.

In this case, when the subscriber responds while receiving a ringing signal (while the telephone is ringing), a DC voltage is obtained across the voltage detection resistor R1 due to the DC current from the power supply 3 and the AC current in the ringing signal. However, this DC voltage is divided by the resistors R7 and R9, and the DC voltage due to the AC current is further divided by the resistor R.
8. It is reduced by capacitor C2 and input to comparator CMP. Comparator CMP operates when this DC current exceeds the reference voltage V _REF .
You can output a signal and check the subscriber's response.

(Effects of the Invention) As explained in detail above, according to the present invention,
A voltage dividing circuit is connected to the subscriber status detection circuit by means of a switch while the subscriber is making a call or sending out a calling signal.
By connecting and disconnecting the low-pass filter, the comparator detects the subscriber's status in two states by one reference voltage, i.e., in the above-mentioned call origination, disconnection, dial pulse reception and ringing signal transmission. Furthermore, the same state detection circuit can detect two input signals having different waveforms and levels with an appropriate detection margin.

[Brief explanation of drawings]

FIG. 1 is a subscriber state detection circuit diagram of an automatic exchange according to the present invention, and FIG. 2 is a similar conventional subscriber state detection circuit diagram. CMP...Comparator, R1...Resistance for voltage detection, Q1...Transistor, C2...Capacitor, R7, R8, R9...Resistor, V _REF ...Setting reference voltage.

Claims (1)

[Claims] 1. A voltage detection resistor provided in a subscriber circuit, a low-pass filter connected to the voltage detection resistor via a switch means that is closed when a ringing signal is generated, and a voltage detection resistor provided in the subscriber circuit; In a subscriber status detection circuit of an automatic exchange equipped with a comparator that compares the detected voltage with a set reference voltage and detects whether the subscriber makes a call, disconnects, receives a dial pulse, or responds to a call, An automatic exchange characterized in that a voltage dividing resistor is connected in a circuit connecting the detecting resistor and the comparator to adjust the difference in voltage detected by the voltage detecting resistor by turning on and off the switching means. Subscriber status detection circuit.