JPH069398B2 - Incoming / outgoing collision detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a terminal device connected to a central office switching facility and having an automatic outgoing call function, in which an outgoing call from the terminal device side and an incoming call from the station side collide. The present invention relates to a call origination / termination collision detection circuit for detecting that.

(B) Conventional Technology As a conventional outgoing / incoming collision prevention circuit, there is one disclosed in Japanese Patent Publication No. 58-37756. In this circuit, a minute electric current is sent to the central line so as not to stop the ringing operation of the central office switching equipment at the time of transmission, and the relay is operated with this minute electric current to prevent collision. A special relay is needed. In addition, the circuit configuration cannot have any function other than the collision monitoring function.

(C) Problems to be Solved by the Invention The present invention solves the problems of the prior art that requires a highly sensitive relay and has only a single function, and is composed of semiconductor parts. The present invention provides an outgoing / incoming collision detection circuit having a calling signal detection function in addition to the incoming call collision detection function.

(D) Means for Solving the Problems The outgoing / incoming collision detection circuit of the present invention is a photo detector in which the polarity of the office line is arranged in the non-conducting direction at the normal time, and the current flowing in the office line is detected in one direction. The light emitting diode (2a) of the coupler and the third resistor (8) connected in series to this light emitting diode (2a)
A series circuit of the capacitor and the capacitor (7), a switch means (6) for forming a line loop connected in parallel to the series circuit, and a first line in which the polarity of the station line is arranged in the conducting direction at the time of transmission. A parallel circuit of a diode (10) and a first resistor (11) is connected in parallel to the line loop forming switch (6), and the light emitting diode (2a) is in a state other than transmission.
A switch means (12) for connecting a second resistor (5) in parallel to the second light emitting diode (2a), which is connected in parallel to the light emitting diode (2a) and limits the forward voltage of the light emitting diode (2a). 4) is provided, and when transmitting at a normal time, a line loop is formed by the parallel circuit of the first diode (10) and the first resistor (11), and the transmission is performed at the time of incoming when the polarity of the station line is reversed. In this case, a minute current is passed through the resistor (11) to the light emitting diode (2a) to detect an incoming / outgoing call, and when a ringing signal is received, the ringing signal is sent to the capacitor (7) and the third resistor (8). ), A current is passed through the light emitting diode (2a) to detect a calling signal.

(E) Action By means of the switch means (12), the first diode (1
0) and the first resistor (11) are connected in parallel to the light emitting diode (2a) and the second diode (4), so if the incoming call collides at the time of outgoing, the
(10) has a reverse bias and cannot conduct. And the first
The resistor (11) allows a current to flow, but limits the flowing current to a current value such that the central office switch does not detect a line loop.
That is, the collision can be detected by the high impedance of the first resistor (11) without closing the line loop.

In addition, since the second resistor (5) is connected in parallel to the light emitting diode (2a) during standby other than the time of transmission, a part of the circuit current flowing at this time is bypassed to the resistor (5). Therefore, the light emitting diode (2a) does not light up at a circuit current below a certain value. In this way, since the resistor (5) can provide the threshold for the detection current, erroneous detection due to noise or the like can be prevented.

(F) Embodiment FIG. 1 is a diagram of an office line circuit of an on-board exchange that uses a call origination / termination collision detection circuit according to an embodiment of the present invention. (A) is an overall circuit diagram, (b)
FIG. 3 is a diagram showing an incoming call detection unit. (1) is a protection circuit that prevents circuit damage due to external surge voltage. (2a) is a light emitting diode of the photocoupler, and (3) is a resistor that limits the current flowing through the light emitting diode. (4) is a light emitting diode (2a)
When a reverse voltage is applied to the light emitting diode (2a)
The zener diode has a function of protecting the light emitting diode (2a) and a function of limiting the voltage applied to the light emitting diode (2a) and the resistor (3) when a forward voltage is applied to the light emitting diode (2a). Reference numeral (5) is a resistor that bypasses the current flowing through the light emitting diode (2a) and the resistor (3) and raises the threshold level of the detected current.

(6) is a relay contact that has the function of generating a dial pulse while forming a loop for a call, and (7) is a DC contact and by combining with the resistance of (8) the relay contact (6) It is a capacitor that also has a protective function. (9) is a transformer that has a balanced / unbalanced conversion function and a loop holding function by passing a DC current. (10) is a diode for making a transmission loop at the time of transmission,
(11) is a resistor for sending a current to the light emitting diode (2a) at the time of an incoming / outgoing collision, and (12) is a resistor (10) and a resistor (10) for making a sending loop or sending a current to the light emitting diode (2a). 11)
Is a relay contact connecting the zener diode (4) and the light emitting diode (2a), (A) is a make side contact, and (B) is a break side contact. This relay contact (12) is on the break side except when transmitting.
It is connected to (B). (2b) is a phototransistor of a photocoupler paired with the light emitting diode (2a), (13) is a pull-up resistor, (14) is an incoming call detection circuit which operates by the detected ringing signal, and a constant voltage (+ 5V) Has been added.

The station line not in the incoming state has a polarity such that L ₁ is ground (0V) and L ₂ is a battery (-48V). On the other hand, office line incoming state, _{L 1} battery (-48V), _{L 2} is earthed (0
The polarity is V). The present invention utilizes this difference in polarity. The operation will be described below.

At the time of transmission, first, the contact (12) outputs a control signal to connect to the make side (A), and the diode (10) and the resistor (11) are made to function. At this time, if the central line is not in the incoming state, the current flows through the next path. L ₁ → Transformer (9) → Diode (10)
→ Contact (12) → Zener diode (4) → L _{2 In} this path, no current flows in the light emitting diode (2a), and collision detection is not performed. The current that flows at this time is sufficient to activate the central office switching equipment. After this, the contact (6) is closed and the contact (1
Return dial 2) to the break side (B) and open / close contact (6) to send a dial pulse.

On the other hand, when the contact line (12) is connected to the make side (A) and the station line is already in the incoming state, the current flows through the next route.

L ₂ → resistance (3) → light emitting diode (2a) → contact (12) → resistance
(11) → Transformer (9) → L (1) Since the value of the resistor (11) determines whether or not a current flows, it is necessary to set the resistance value so that the current flows through the upper path. When a current flows, as a result, the phototransistor (2b) shifts from the cutoff state to the conduction state, and the potential at the point C in FIG. 1 (b) becomes 0V.
Therefore, the outgoing / incoming collision detection means (for example, CPU) detects the incoming / outgoing collision when the potential at the point C changes from 5V to 0V. After the detection, the vacant station line is searched for and the call is transmitted.

If the value of the resistor (11) is too small, the ringing operation of the central office switching equipment will be stopped, so in the end, the phototransistor (2b)
The value of the resistor (11) must be set so as not to stop the ringing operation of the central office switching equipment while at the same time supplying a sufficient current to the light emitting diode (2a) so as to bring the switch into a conductive state. By setting the resistance (11) to an appropriate value as described above, it is possible to activate the central office switching equipment if it does not collide with the incoming call.

In the case of a collision with an incoming call, no current flows through the diode (10). Therefore, at this time, since only a small loop current flows through the resistor (11), the station switching equipment does not detect the line loop and does not stop the calling operation.

At this time, a current flows through the light emitting diode (2a) to detect the inversion of the line polarity (B line battery), so the control system circuit (not shown) immediately stops the transmission process of the line and processes the incoming call. I do.

Next, the incoming response detection function of this circuit will be described.
After making a dial loop at dialing and sending dial pulse,
While waiting for a response from the called party, the central office switching equipment operates to reverse the polarity of the originating station line when the called party answers. As a result, current flows through the circuit through the following three paths.

L ₂ → Zener diode (4) → Contact (6) → Transformer
(9) → L ₁ L ₂ → resistance (3) → light emitting diode (2a) → contact (6) → transformer (9) → L ₁ L ₂ → resistance (5) → contact (12) → contact (6) → Transformer (9) →
L ₁ As a result, the phototransistor (2b) shifts from the cutoff state to the conduction state as shown in (b) of FIG. 1, and the incoming call response is detected as described above. The incoming call response is used for providing billing information.

Next, the call signal detection function of this circuit will be described.
When receiving a call, a call signal of 16 Hz, 75 Vrms is sent to L ₂ from the central office switching equipment. Since the contact (6) is open, it is insulated in terms of direct current, but the capacitor (7) forms a loop in terms of alternating current, so the ringing signal passes through.
When this calling signal causes L ₂ to have a higher potential than L ₁ , a current flows through the light emitting diode (2a), and as a result, the phototransistor (2b) shifts from the cutoff state to the conductive state. When the potential of L ₁ is higher than that of L _2, no current flows in the light emitting diode (2a), and as a result, the phototransistor (2b) returns to the cutoff state. In other words, the phototransistor (2b) has 16
Conduction and interruption are repeated at a frequency of Hz, and this phenomenon is detected by the incoming call detection circuit (14) shown in (b) of FIG. This incoming call detection circuit is configured by using, for example, a counter circuit.

Here, the resistor (5) is used to bypass the current flowing through the light emitting diode (2a) and the resistor (3) and raise the threshold level of the detected current. It has a function to prevent false detection. However, the function to detect the above-mentioned incoming call has a light emitting diode (2a)
In the case where the resistor (5) is attached, the current flowing in the light emitting diode (2a) is limited by the resistor (11), and its value is very small.
The current does not flow to the terminal and the incoming call cannot be detected sufficiently. Therefore, when detecting incoming and outgoing collisions, use the contact (12) to connect the resistor (5).
Is cut off, and all the minute current flowing between L ₂ and L _{1 is made} to flow through the light emitting diode (2a). As a result, the threshold level of the detection current is lowered. In addition, Zener diode
A diode may be used instead of (4).

As described above, according to the present invention, since the incoming / outgoing collision detection circuit can be configured by the semiconductor parts, a highly sensitive relay is not required, and the ringing signal detection and the incoming call response detection functions can be provided.

(G) Effect of the Invention The outgoing / incoming collision detection circuit of the present invention can detect a ringing signal and can prevent malfunction due to external noise of the ringing signal.

[Brief description of drawings]

FIG. 1 is a diagram of a central office line circuit of a private branch exchange using the outgoing / incoming collision detection circuit of the present invention, in which (a) is an overall circuit diagram and (b) is a diagram showing an incoming call detection unit. FIG. 2 is a diagram showing the flow of the circuit current (loop current) during normal transmission. FIG. 3 is a diagram showing a flow of a circuit current (loop current) at the time of a call origination / termination collision. (1) …… Protection circuit, (2a) …… Light emitting diode, (2b) ……
Phototransistor, (3), (5), (8), (11), (13) ……
Resistance, (4) …… Zener diode, (6), (12) …… Relay contact, (7) …… Capacitor, (9) …… Transformer, (10)
Diode, (14) …… Incoming call detection circuit.

Claims (2)

[Claims] 1. In a call origination / termination collision detection circuit of a terminal device having both outgoing and incoming functions for a station line, the polarity of the station line is arranged in a non-conducting direction in a normal state and flows to the station line. Photocoupler light emitting diode (2a) that detects current in one direction, and third resistor (8) connected in series with this light emitting diode (2a)
A series circuit of the capacitor and the capacitor (7), a switch means (6) for forming a line loop connected in parallel to the series circuit, and a first line in which the polarity of the station line is arranged in the conducting direction at the time of transmission. A parallel circuit of a diode (10) and a first resistor (11) is connected in parallel to the line loop forming switch (6), and the light emitting diode (2a) is in a state other than transmission.
A switch means (12) for connecting a second resistor (5) in parallel to the second light emitting diode (2a), which is connected in parallel to the light emitting diode (2a) and limits the forward voltage of the light emitting diode (2a). 4) is provided, and when transmitting at a normal time, a line loop is formed by the parallel circuit of the first diode (10) and the first resistor (11), and the transmission is performed at the time of incoming when the polarity of the station line is reversed. In this case, a minute current is passed through the resistor (11) to the light emitting diode (2a) to detect an incoming / outgoing call, and when a ringing signal is received, the ringing signal is sent to the capacitor (7) and the third resistor (8). A calling signal is detected by passing a current through the light emitting diode (2a) via the (1). 2. The outgoing / incoming collision detection circuit according to claim 1, wherein the second diode (4) is a Zener diode.