JPS6255342B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ring trip circuit used when calling a subscriber of a telephone exchange.

A ring signal current is sent from the telephone exchange to the called subscriber, and when the called subscriber answers, the call current loop is closed, so this call current is detected and the sending of the ring signal current is stopped. The so-called ring trip circuit has been known for a long time. Conventional circuits using electromagnetic relays and electronic circuits (for example, Japanese Patent Publication No. 44-24535) are known. Those that use electromagnetic relays have an AC insensitive relay inserted in the signal line of the called party, and are configured to detect when the called party responds and DC communication current begins to flow. It is what was done. The conventional electronic circuit is a miniaturized version of this, which detects the current in the called party's signal line via a low-frequency device, and uses a transistor switch that operates only on direct current. It is something. However, the conventional method described above uses the principle of attenuating the sensitivity to AC components in some way to discriminate the DC component, and it is impossible to simultaneously improve the sensitivity to AC components and the sensitivity to DC components. Ta. For this reason, if the line resistance of the accommodated subscriber exceeds a certain level, the DC component current that flows when the called party answers becomes small, so the relay cannot reach the desired value, and the called party has many telephones connected in parallel. If it is connected, the AC component current will become excessive and the relay will be touched when the called party does not respond.
The range of external circuit conditions under which a normal ring trip can be performed is narrow, making it inconvenient to use.

To solve these problems, a ring trip circuit was proposed in Japanese Patent Laid-Open No. 56905/1983. A basic circuit diagram of this ring trip circuit is shown in FIG. In the figure, R1 is an insertion resistor for signal detection.
R2 is an overcurrent limiting resistor, C1 is a positive voltage charging capacitor, C2 is a negative charging capacitor,
R3 and R4 are resistors for sum voltage synthesis, C3 is a smoothing capacitor, R5 is a discharge resistor, Q1 is a transistor, ZD1 is a constant voltage diode, and D1 and D2 are diodes. Also, F1 is an auxiliary relay, f1
is the F1 contact, G1 is the ring trip relay, g
1 indicates the contact point of G1, respectively.

In this method, the positive and negative voltages of the signal detected by resistor R1 are charged to separate capacitors C1 and C2, respectively, and a sum voltage of an appropriate ratio is calculated from the charging voltages of both capacitors to R3 and R4. When the called party answers, the sum voltage exceeds a certain value due to the superposition of DC components, and this is sensed and a ring trip is performed.

In Figure 1, before the called party answers,
The signal component is only an intermittent 16Hz alternating current component, and the signal is symmetrical in sign and negative. Therefore, the absolute values of the charging voltages of the capacitors C1 and C2 in the positive and negative directions are equal. If the resistance values of the resistors R3 and R4 are made equal here, the voltage generated at the midpoint M becomes zero, so that there is no base current and no collector current of the transistor Q1. Then, when the called party answers,
Since a DC component is superimposed on the detection signal from the resistor R1, the positive direction voltage increases significantly. Therefore, the absolute value of the positive charging voltage of capacitor C1 becomes larger than the negative charging voltage of capacitor C2, and a positive voltage proportional to the DC component of the signal line appears at midpoint M. Therefore, the base current and collector current of transistor Q1 flow, and a ring trip operation is performed.

According to the method shown in FIG. 1, the alternating current component and the direct current component of the signal can be strictly distinguished, so that the restrictions on external circuit conditions are significantly relaxed compared to the conventional method of attenuating the alternating current component. However, this method has the following drawbacks. First, a certain degree of accuracy is required in the configuration of the resistance combining circuit and the like that generates the sum voltage. This corresponds to the resistance values of R3 and R4 in FIG. Second, the voltage of the detected DC component is small.
For example, in Figure 1, the charging voltage of capacitor C1 is +V2 and the charging voltage of capacitor C2 is -V2.
V3, the voltage appearing at the midpoint M is (V2−
V3)/2.

An object of the present invention is to solve the various drawbacks of the conventional ring trip circuit as described above, and to provide a ring trip system that is easy to manufacture and reliable in operation.

The ring trip circuit of the present invention includes: a ring signal detection resistor inserted in series on a ring signal line; a series circuit of a first diode and a second diode connected in parallel to the ring signal detection resistor; a series circuit of a third diode and a first capacitor connected in parallel to the diode; a series circuit of a fourth diode and a second capacitor connected in parallel to the second diode; and the fourth diode set and the second and third diode sets have the same polarity, and the polarities of both diode sets are opposite, and one of the first capacitor and the second capacitor, respectively. The terminal is connected to the connection point between the first diode and the second diode, and
The present invention is characterized in that an optical coupling element is connected between the other terminals of the first capacitor and the second capacitor, respectively.

When the called party answers, a direct current component is superimposed on the calling signal, so that the magnitudes of the positive and negative voltages of the signal are no longer equal. Therefore, if the positive direction voltage and the negative direction voltage are collected using a pair of capacitors in the same direction, a large potential difference will appear between the two collected values. The present invention identifies the presence or absence of a response from the called party by reading this potential difference.

FIG. 2 shows a principle circuit diagram of an embodiment of the present invention. In the figure, R6 is an insertion resistor R7 for signal detection, R10 is an overcurrent suppression resistor, and C4 is for charging the absolute value of negative direction voltage. Capacitor, C5 is a capacitor for positive voltage charging, R8, R9, R11 is a discharge resistor, PC is an optical coupling element, ZD2 is a constant voltage diode, D3, D4, D5, D6 are diodes, F2
is an auxiliary relay, f2 is a contact of F2, G2 is a ring trip relay, and g2 is a contact of G2.

In Figure 2, before the called party answers,
The component of the detection signal by the resistor R6 is only an intermittent 16 Hz alternating current component, and its polarity is symmetrical. Therefore, since the voltages charged in the capacitors C4 and C5 are almost equal, no potential difference occurs between points X and Y, and no current flows through the diode side of the optocoupler PC, so that the relays F2 and G2 does not work. Next, when the called party answers, a DC component is superimposed on the detection signal from the resistor R6, so that the positive voltage increases significantly. Therefore, the voltage charged to the capacitor C5 becomes much larger than the voltage charged to the capacitor C4, and the voltage charged to the capacitor C5 becomes much larger.
A large potential difference occurs between Y. Therefore, a current flows through the diode side of the opto-coupler PC, and the transistor side of the opto-coupler PC becomes conductive, operating the relays F2 and G2 and performing a ring trip.

In this embodiment, when the calling AC signal is interrupted before the called party responds, a positive voltage initially appears across the resistor R6 depending on the phase. A positive potential difference may occur between the two. For this purpose, capacitor C6, constant voltage diode
ZD2 is provided to prevent malfunctions from occurring due to transient phenomena, noise, etc.

As described above, according to the present invention, the execution of the ring trip is determined by determining the magnitude of the difference in potential between the X point and the Y point resulting from the charging voltage of the capacitors C5 and C4. Since the direct current component and the direct current component can be strictly distinguished, restrictions on external circuit conditions are significantly relaxed compared to conventional methods.

Also, compared to the method shown in Figure 1, the first
There are no delicate parts such as the resistor combination circuit in the figure where the precision of the components is a problem. Second, the voltage detected due to the superposition of the DC component when the called party responds is relatively large. That is, the voltage at point X is +
Assuming that the voltage at V2 and point Y is +V3,
The potential difference between points X and Y to be determined is (V2-
V3), which is twice that of the case in Figure 1.

Although this embodiment embodies the present invention using a pure circuit method, it is also possible to realize the present invention using a software method in electronic exchanges, which have been increasingly adopted in recent years. be. That is, the signal voltage in the positive and negative directions is sampled every half cycle of the calling AC signal, and after digitizing it by A-D conversion, the difference between the absolute values of the two is calculated by the processing device, and the numerical value is calculated. Possible methods include determining the presence or absence of DC component superimposition based on the magnitude. Further, in this case, as a method for detecting the difference between both absolute values, in addition to the method using subtraction, it is also possible to use weeding or the like.

As explained above, the present invention has the effect of easily realizing a ring trip circuit that can determine the superposition of a DC component on a calling signal line more strictly than any existing method.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an improvement that has already been proposed for a conventional ring trip circuit, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. R6...Insertion resistor for signal detection, R7, R10...
...Overcurrent suppression resistor, R8, R9, R11...Discharge resistor, C4...Capacitor for charging the absolute value of negative direction voltage, C5...Capacitor for charging positive direction voltage,
PC...Optical coupling element, ZD2... Constant voltage diode, D3, D4, D5, D6... Diode, F
2...Auxiliary relay, f2...F2 contact, G2...
...Ring trip relay, g2...G2 contact.

Claims (1)

[Claims] 1. A calling signal detection resistor inserted in series on a calling signal line; a series circuit of a first diode and a second diode connected in parallel to the calling signal detection resistor; a series circuit of a third diode and a first capacitor connected in parallel to the diode; a series circuit of a fourth diode and a second capacitor connected in parallel to the second diode; and the fourth diode set and the second and third diode sets have the same polarity, and the polarities of both diode sets are opposite, and one of the first capacitor and the second capacitor, respectively. The terminal is connected to the connection point between the first diode and the second diode, and
A ring trip circuit characterized in that an optical coupling element is connected between the other terminals of the first capacitor and the second capacitor.