JPS5940340B2 - ring trip circuit - Google Patents

Description

[Detailed description of the invention] The present invention relates to telephone exchanges.

In particular, the ringing signal current (e.g. 16
This invention relates to a ring trip circuit that stops the intermittent alternating current (H2) in response to a response from a called subscriber. The principle circuit diagram of a conventional ring trip circuit is shown in FIGS. 1 and 2.

FIG. 1 shows a circuit that uses a relay directly to identify the response of a called party and has been known for a long time. In the figure, F1 represents an AC non-sensing relay, fl represents a contact of F1, G1 represents a ring trip relay, and gl represents a contact of G1. In the circuit shown in FIG. 1, relay F1 is activated only when a DC component appears in the signal due to the response of the called party, thereby activating relay G1 to perform a ring trip. The contact is a recovery contact. The circuit shown in Figure 2 is a combination of a low-pass filter and a transistor switch.
4535.

In the figure, R1 is an insertion resistor for signal detection, R2 is a low-pass filter configuration resistor, C1 is a low-pass filter configuration capacitor, Q1 is a transistor, ZDI is a constant voltage diode, F2 is an auxiliary relay, f2 is a contact of F2, and G2 is a ring. Trip relay, g2 represents the contact point of G2. In the circuit of FIG. 2, the alternating current component of the signal detected by resistor R1 is attenuated by a low-pass filter composed of resistor R2 and capacitor C1. On the other hand, if an appropriate operating threshold value is set for transistor Q1 using Zener diode ZDI, relays F2 and G2 will be activated only when the called party answers and a DC component is superimposed on the signal. It is possible to perform a ring trip. In the circuit shown in Figure 1, when external resistance such as line resistance exceeds a certain level,
When the called party responds, the DC current flowing through the relay F1 may not reach its current value, making ring trip impossible.

Furthermore, if a large number of telephones are connected in parallel to the called party, the alternating current flowing through the relay F1 becomes excessive, and the relay F1 may be affected by only the alternating current, resulting in a malfunction. In addition, although the circuit shown in Figure 2 alleviates the drawbacks of the circuit shown in Figure 1, the operating principle of attenuating the AC component and distinguishing the DC component remains the same; has the disadvantage that sensitivity to DC components must be sacrificed.

In this way, in the conventional ring trip circuit, it is theoretically impossible to simultaneously improve the sensitivity to AC components and the sensitivity to DC components, and the line resistance of the accommodated subscribers is limited. The number of telephones that can be connected to one subscriber is limited to a small number, and the range of external circuit conditions that can perform a normal ring trip is narrow, making it inconvenient to use. The present invention provides an electronic circuit for detecting the DC component of the signal line when a called party responds, and makes the sensitivity more pure for AC components and more sensitive for DC components. It is an object of the present invention to provide a circuit which overcomes the drawbacks and can be used under a much wider range of external circuit conditions than conventional devices.

The present invention includes a resistor inserted in series in a path of direct current flowing through the subscriber line when the subscriber line is closed;
The circuit for detecting the terminal voltage of the resistor and performing the ring trip operation is connected to the ring trip circuit, and the circuit for performing the ring trip operation includes a first capacitor that charges only the positive voltage of the terminal voltage of the resistor. and,
It is characterized by including a second capacitor that charges only the negative direction voltage of the terminal voltage, and a circuit that performs a ring trip operation when the sum of the charging voltages of the first hexagram and the second capacitor exceeds a certain value. shall be. The present invention uses the circuit shown in Fig. 1, in which seven resistors for signal detection are inserted in the position where the relay F1 is inserted, and the positive direction voltage and negative direction voltage of the detected signal are charged to separate capacitors. Then, a sum voltage of an appropriate ratio is extracted from the charging voltages of both capacitors by resistance composition, etc., and when the called party answers, the sum voltage exceeds a certain value, so this is sensed and a ring trip is performed. Features. When the called party answers, a DC component appears in the signal current, so the magnitudes of the positive and negative voltages of the signal are no longer equal, so the sum of the positive and negative voltages extracted from a pair of charged capacitors is The voltage also fluctuates significantly compared to before the called party answers.

The present invention allows the called party's response to be identified by reading the variation in this sum voltage. FIG. 3 is a circuit diagram showing one embodiment of the present invention.

In the figure, R3 is a resistor inserted for signal detection, R4 is a resistor for overcurrent suppression, C2 is a capacitor for positive direction voltage charging, C3 is a capacitor for negative direction charging, and R5 and R6 are sum voltage composition. C4 is a smoothing capacitor, and R7 is a discharge resistor. Q2 is a transistor, ZD2 is a constant voltage diode, and Dl, D2, and D3 are diodes.
F3 is an auxiliary relay, F3 is a contact of F3, G3 is a ring trip relay, and G3 is a contact of G3. Resistor R3 is inserted in series with the power supply -48V via contact G3. Of the voltage generated in this resistor R3, the positive voltage is transferred to the capacitor C2 by resistor R4 and diode D1.
, and a negative voltage is applied to the capacitor C3 by means of a resistor R4 and a diode D2 connected in the opposite direction to the diode D1. Two resistors R of equal value are connected between these two capacitors C2 and C3.
5 and R6 are connected in series and coupled, and the potential at this coupling point M is led to the base of transistor Q2. Further, a parallel circuit including a capacitor C4 and a resistor Rr is inserted between this node M and the power source -48. The emitter circuit of the transistor Q2 is connected to a power source -48 via a constant voltage diode ZD2, and a parallel circuit of a relay F3 and a diode D3 is inserted between the collector and ground. The operation of the circuit configured in this way will be explained using the operation waveform diagram shown in FIG. 4.

FIG. 4 shows the voltage waveform of the signal detected by the resistor R3 shown in FIG. 3, with A representing before the called party answers and B representing after the called party answers. First, before the called party answers, the signal component is only an intermittent 16 Hz alternating current component, and the signal is symmetrical in sign as shown in FIG. 4A.

Therefore, the absolute values of the charging voltages in the positive and negative directions of capacitors C2 and C3 are equal. Therefore, a voltage proportional to the sum of the voltages of both capacitors C2 and C3 generated at the midpoint M by the resistors R5 and R6 becomes an atmosphere, so that there is no base current of the transistor Q2 and no collector current flows. Therefore, relay F3 does not operate. Of course, depending on the phase when the ringing signal is applied, a positive voltage may first appear across the resistor R3, and a positive voltage temporarily appears at the midpoint M, causing the operation threshold by the voltage regulator diode ZD2 to rise. There is a risk that relay F3 will operate when the value is exceeded. For this reason, in the circuit of this embodiment, a capacitor C4 is provided to make the rise of the voltage at the midpoint M more gradual, so as to prevent malfunctions from occurring due to these transient phenomena and other noises. Next, when the called party answers, a DC component is superimposed on the signal detected by resistor R3, so that the positive voltage increases significantly as shown in FIG. 4B.

Therefore, the absolute value of the positive charging voltage of capacitor C1 becomes larger than the negative charging voltage of capacitor C2, and the voltage proportional to the sum voltage appearing at midpoint M becomes a positive voltage. When this voltage exceeds the operating threshold of the constant voltage diode ZD2, the relay F3 is activated and a ring trip operation is performed. Even if the external resistance such as the line resistance of the subscriber line is large and the positive voltage that appears at the midpoint M when the called party goes off-hook is small, the circuit of the present invention applies the voltage at the midpoint M only when the called party responds. Since the voltage becomes positive, the constant voltage diode ZD2 can be chosen so that the threshold value is quite small. In this way, compared to conventional circuits that attenuate AC components, the circuit of the present invention can strictly distinguish between AC and DC components of a signal, and can extremely sensitively sense the presence of DC components, making it possible to detect changes in external circuit conditions. Restrictions are significantly relaxed compared to the past.

This circuit allows a large number of telephones to be connected to one subscriber, and since it operates normally even in the presence of considerable line resistance, it is possible to accommodate subscribers over considerable distances. As explained above, the present invention provides a ring trip circuit that is unlikely to cause malfunctions due to alternating current components of signals, is sensitive to direct current components, and can withstand wide variations in external circuit conditions.

[Brief explanation of drawings]

1 and 2 are circuit diagrams of conventional ring trip circuits. FIG. 3 is a circuit diagram of an embodiment of the present invention. FIG. 4 is a voltage waveform diagram appearing across the resistor R3 shown in FIG. 3, where A is before the called party responds and B is after the called party responds. F1... AC non-sensing relay, f1... Contact of F1, F2, F
3...Auxiliary relay, F2, f3...F
2, F3 contact, Gl, G2, G3... Ring trip relay, Gl, g2, g3... Gl
, G2, G3 contacts, k...Recovery contact, Rl
, R3... Insertion resistor for signal detection, R2...
...low-pass filter configuration resistor, C1...low-pass filter configuration capacitor, Ql, Q2...transistor, ZDl, ZD2...constant voltage diode,
R4... Overcurrent suppression resistor, C2... Capacitor for positive voltage charging, C3... Capacitor for negative voltage charging, R5, R6... Sum Voltage composite resistance, C4...Smoothing capacitor, R7...
...discharge resistance.

Claims (1)

[Claims] 1. A resistor R_3 inserted in series in the path of direct current flowing through the subscriber line when the subscriber line is closed;
In a ring trip circuit equipped with a circuit that detects the terminal voltage of this resistor and performs a ring trip operation, the circuit that performs the ring trip operation has a first circuit that charges only the positive direction voltage of the terminal voltage of the resistor. Capacitor C
_2, a second capacitor C_3 that charges only the negative terminal voltage, and a circuit that performs a ring trip operation when the sum of the charging voltages of the first and second capacitors exceeds a certain value. A ring trip circuit comprising: