JPH0583752A - Electronic processing choke circuit with dial pulse transmission function - Google Patents

Abstract

PURPOSE:To prevent discharge of a capacitor in an electronic processing choke circuit with an inexpensive semiconductor component. CONSTITUTION:The electronic processing choke circuit in which a transistor(TR) 3 and a resistor 6 used to give a bias between a base and a collector of the TR 3 are connected and a capacitor 5 interrupting an AC component is connected between the base and an emitter of the TR 3 and a station exchange simulation circuit 1 is connected between the collector and the emitter of the TR 3 is provided with a TR 4 interrupting a collector current of the TR 3 and with a photocoupler 7 located between a connecting point of a negative pole of a DC power supply and the capacitor 5 and the emitter of the TR 3 and used to interrupt a DC current when the TR 4 interrupts the collector current of the TR 3 so that the ON/OFF operation of a dial signal reception photocoupler 2 and the discharge prevention photocoupler 7 are implemented alternately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic choke circuit with a dial pulse transmitting function for a PBX equipment central line trunk. The central line trunk of the PBX device has a function of loop-connecting to a central office switch to relay dial pulses of the calling subscriber. FIG. 4 shows an example of the connection configuration of the trunk line trunk of the PBX device.
Shown in. In the figure, 31 is a PBX, 32 is a trunk line trunk,
33 is a network, 34 is a central control unit, 35 is a subscriber circuit, 36 is a subscriber terminal, 37 is a central office switch, and 38 is a central office line.

A subscriber circuit 35 of the PBX 31 is activated by a call from a subscriber terminal 36, and in the case of connection via a central office switch 37, a central line control unit 34 controls the central line trunk 32 connected to a network 33. To do. The office line trunk 32 forms a loop circuit with respect to the office line 38 and activates the subscriber circuit of the central office exchange 37. PBX by dialing the subscriber terminal 36
The loop circuit of the office line trunk 32 is turned on / off under the control of 31. A connection signal is sent to the central office exchange 37 by this ON / OFF signal, and the incoming call is connected to the corresponding subscriber or the subscriber who relays the exchange.

The office line trunk 32 is composed of a contact a which forms a loop circuit and relays a dial pulse, and a point b which connects a voice circuit simultaneously with the formation of the loop circuit and releases it during the dial pulse. The contact b is a station. It is used to relay the dial tone upon connection from the exchange 37 to the calling subscriber and to eliminate noise in the dial pulse. The contact a is composed of an electronic choke circuit, and is composed of an electronic component having a low impedance for a direct current and a high impedance for an alternating current. This is because the impedance is high during a call and low during dialing.

[0004]

2. Description of the Related Art FIG. 5 shows a circuit configuration diagram of a computerized choke circuit having a dial pulse transmitting function of Conventional Example 1. In the figure, 21 is a switching center pseudo circuit, 22 is a dial signal receiving circuit, 23 is a dial pulse sending transistor Tr1, 24
Is the transistor Tr2 for controlling the base current of Tr1, 25 is the capacitor C1 for choke circuit, and 26 is the resistor R1 for choke circuit.

The pseudo-circuit 21 of the central office is composed of a DC power source V0 and a load resistor R0.
Shows a pseudo circuit equivalent to 0 Ω, dial signal receiving circuit
Reference numeral 22 is a photocoupler PcI, which is on / off controlled by a dial signal DP from the control device. Transistor
Tr1 sends a dial pulse to the central office side by turning on / off the collector current Ic. Transistor Tr2 is for controlling the base current of transistor Tr1.
It is controlled by turning Pc1 on and off.

FIG. 6 shows a timing chart of the circuit operation of the conventional example 1 described above. The figure shows ON / OFF of the signal DP from the controller
Off, photo coupler Pc1 on / off, transistor Tr
2 shows a timing chart of the on / off of 2, the voltage across capacitor C1, the on / off of transistor Tr1, and the collector current Ic. A represents a waveform when a loop is formed and B represents a waveform when a dial pulse is transmitted.

The circuit operation of the first conventional example will be described with reference to FIGS. When the signal DP is 0, Pc1 is turned on and Tr2 is turned off because Tr2 is not biased. Since Tr2 is off, there is no DC bias applied to Tr1.
Turns off and Ic does not flow. At this time, there is a route for direct current to flow through Pc1 and R5, but normally R4 is several hundred KΩ to several MΩ, and it can be said that almost no current flows. Next, when DP becomes 1 when the A loop is formed, Pc1 is turned off, and Tr2 is turned on by applying a DC bias to the resistor R4.

Next, it is the turn-on of Tr1, but since the charging current flows to C1, Tr1 is charged with C1 and the voltage across it is Tr.
Do not turn on until the bias voltage reaches 1. This is shown in the timing chart of FIG. 6, but since the collector current Ic actually flows, the bias voltage of Tr1 also changes and the simple on / off does not occur as shown in the figure, but the bias to Tr1 is delayed. Next, when DP becomes 0 again, Tr2 is turned off, and the charge stored in the capacitor C1 is R3 and Tr1,
It is discharged through R2. Here by the B dial pulse
When DP becomes 1, the delay operation of t as described above is performed. Here, DP = 0 represents a break of the dial pulse, and DP = 1 represents a make of the dial pulse.

As described above, in the circuit of the conventional example 1, a gap of the time t between the control signal DP and the actual dial pulse signal Ic occurs due to the charging of the capacitor C1. FIG. 7 and FIG. 8 show a circuit configuration diagram and an operation timing chart of Conventional Example 2 used to solve this problem. Figure 7
The circuit is a relay to the capacitor discharge circuit of the conventional example 1 in FIG.
This is a circuit with RL27 added. The signal rl is a signal for controlling the relay RL, and when rl = 1, the relay RL operates and closes. When rl = 0, the relay RL is restored and released.

Timing chart In FIG. 8, the relay
When the RL is operating, it is exactly the same as the case of the conventional example 1. That is, DP changes from 0 to 1. This corresponds to off-hook in the trunk line trunk circuit. At this time, since the charging current flows to C1, Ic is delayed by t as shown in the figure. However, even if this t is several tens of ms, there is no problem in the actual operation, so this delay can be ignored. Next, at the time of dial pulse transmission, that is, during tDP, rl changes from 1 to 0 and RL is restored. Therefore, the charge charged in C1 remains as it is without a discharge route.

On the other hand, since C1 is separated by RL,
Since Tr1 is directly biased by R1, the operation of Tr2 becomes the operation of Tr1 as it is, and the dial pulse is sent without any delay. Next, when dial pulse transmission is completed RL
However, the charge current does not flow in C1 and Tr1 remains on because the charge remains in C1 without being discharged.

According to the technique of the second conventional example, a capacitor connected in order to prevent AC bias from being applied between the base and emitter of a transistor for flowing a direct current in an electronic choke circuit is connected to both ends of C1 at the time of dial pulse transmission. Since the delay of the pulse current is prevented by disconnecting either one or both of them, there is a drawback that only mechanical parts such as a relay can be used as a disconnecting means. This is because when semiconductor parts are used as a means for disconnecting, a circuit that always supplies a direct current is necessary.

FIG. 9 is a circuit configuration diagram of Conventional Example 3 in which a semiconductor component is used instead of a relay for preventing discharge of a capacitor.
Shown in. This is the case where the photocoupler 28 is used as a semiconductor component, and a circuit such as a resistor R6 that always sends a direct current to the photocoupler Pc2 is required, and the electric charge of C1 is discharged through this R6. It becomes the same as the case of 5.

[0014]

As described above, when there is no capacitor discharge prevention circuit of the conventional example 1, the dial pulse is distorted, and a mechanical component such as a relay is used in the capacitor discharge prevention circuit of the conventional example 2. In that case, there is a drawback that it is more expensive than a semiconductor component, has a large weight and volume, and requires a large current for operation. When semiconductor components are used instead of relays, a circuit for passing a DC current is required as in the case of the conventional example 3, and as a result, the same problem as in the conventional example 1 occurs.

It is an object of the present invention to construct a computerized choke circuit which does not cause a delay of dial pulse, while using only semiconductor parts without using mechanical parts in order to disconnect the discharge route of the capacitor. ..

[0016]

FIG. 1 is a block diagram showing the principle of the present invention. In the figure, reference numeral 1 is a pseudo-circuit of a central office switch composed of a DC power source V0 and a load resistance R0, 2 is a photo coupler Pc1 for receiving a dial signal DP1, 3 is a transistor Tr1 for sending a dial pulse, and 4 is a transistor Tr for controlling a base current of Tr1.
Reference numerals 2 and 5 indicate a choke circuit capacitor C1, 6 indicates a choke circuit resistor R1, and 7 indicates a discharge preventing photocoupler Pc2.

A resistor 6 for biasing the transistor 3 and a base and a collector of the transistor 3 is connected to prevent the transistor 3 from being biased in an alternating current between the base and the emitter of the transistor 3. A dial constructed by connecting a capacitor 5 so that the collector side of the transistor 3 is connected to the positive side of the DC power supply of the PBX pseudo circuit 1 and the emitter side of the transistor is connected to the negative side of the DC power supply of the PBX pseudo circuit 1. In the electronic choke circuit with a pulse sending function, the transistor 3
To the capacitor 5 and the negative side of the DC power source, a photocoupler 7 for blocking the collector current is provided for blocking the DC current when the transistor 4 blocks the collector current of the transistor 3. On / off of the dial signal receiving photocoupler 2 and the discharge preventing photocoupler 7 which are provided between the connection point and the emitter of the transistor 3 and control the on / off of the transistor (4).
The off operation is configured to be opposite to each other.

[0018]

The operation timing chart of the present invention is shown in FIG. In the figure, is the dial signal DP1, is the on / off state of the photocoupler Pc1, is the on / off state of the transistor Tr2, is the negative signal DP2 of the dial signal DP1,
Is the on / off state of the photocoupler Pc2, is the capacitor
The voltage across C1 indicates the on / off state of the transistor Tr1, and indicates the current state of the collector current Ic of the transistor Tr1. The dial signal DP1 is sent by 1 at the time of forming the loop circuit at the time of connection and A at the time of sending the dial pulse by alternately repeating 0 and 1 under the control of the control device. The dial pulse break is represented by 0, and the dial pulse make is represented by 1. The photocoupler Pc1 turns on when the dial signal DP1 is 0, and turns off when the dial signal DP1 is 1. The transistor Tr2 is turned off when the photocoupler Pc1 is on, and turned on when the photocoupler Pc1 is off to control the base current of the transistor Tr1. The negative signal DP2 of the dial signal is a negative signal of the dial signal DP1 and is sent from the control device so that it becomes 0 when DP2 is 1 and becomes 1 when DP2 is 0. The photocoupler Pc2 turns off when the signal DP2 is 1, and turns on when the signal DP2 is 0. Therefore photo coupler
The opposite of Pc2 on / off. The voltage across the capacitor C1 starts to be charged when the transistor Tr2 is turned on at the time point A when the loop circuit is formed, and ends when the bias voltage of the transistor Tr1 is reached.
The charging time is t. At the time of dial pulse transmission B, since the photocoupler Pc2 is also off when the transistor Tr2 is off, the capacitor C1 remains charged without a discharge circuit being formed during the dial pulse transmission. The transistor Tr1 turns on after the time t, but at the time of dial pulse transmission B, the transistor Tr1 also turns off / on according to the turning on / off of the transistor Tr2. Therefore, the collector current Ic of the transistor Tr1 also flows according to the dial pulse DP1 and sends the dial impulse to the central office side without delay.

[0019]

FIG. 3 shows a circuit configuration diagram of an embodiment of the present invention.
In the figure, 11 is a control device, 12 is a dial signal sending circuit, 13 is a local exchange pseudo circuit, and 14 is an electronic choke circuit with a dial pulse sending function. Pc1 and Pc2 are photocouplers, Tr1 and Tr2 are transistors, C1 is a capacitor, and R1, R2, R3, R4 and R5 are resistors. Central office switching circuit 13
Consists of DC power supply V0 and load resistance R0, V0 is usually 48V, and R0 is generally 400Ω. Dial signal transmission circuit
12 is a computerized choke circuit that creates a positive DP1 signal and a negative DP2 signal by a TTL circuit according to a control signal from the controller 11.
Supply to the rectifier section of 14 photocouplers Pc1 and Pc2.

In the electronic choke circuit 14, the signal DP1
Is the control signal of Pc1, the signal DP2 is the control signal of Pc2, and D
When P1 and DP2 are 0, Pc1 and Pc2 are on and 1
It turns off when. The logic of DP1 and DP2 is opposite when sending a dial pulse. In other words, during dial pulse transmission, Pc2 is controlled to be on when Tr2 is on and off when Tr2 is off. In this plan, only this dial pulse is specified and the others are not covered by this plan, but it is common sense that both Tr2 and Pc2 are turned on during off-hook and turned off during on-hook.

First, it is assumed that no charge is stored in the capacitor C1. Also, since DP1 and Tr2 operate in exactly the same way except that the logic is reversed, only the operation of Tr2 will be described.
Tr2 and Pc2 are initially off because they are off-hook. Next, at transmission, both Tr2 and Pc2 are turned on, and the charging current flows in C1. Here, when Tr2 and Pc2 are turned on and before Tr1 is turned on, t
However, there is usually no delay. Next, the process proceeds to dial pulse transmission, but since Pc2 repeats on / off in synchronization with Tr2, the charge charged in C1 remains charged without a discharge route, and Tr2, Pc is recharged.
Since C1 is fully charged even when 2 is turned on, Tr1
Is turned on and off repeatedly without being delayed by C1 and controlled by Tr2 without delay. Pc2 can be replaced by a relay, but using an inexpensive photocoupler is more advantageous.

The resistor R2 may be deleted, and the circuit in which the resistor R3 is deleted functions in exactly the same manner. Further, it is also applied to a circuit which cuts out both the base and collector currents and sends a dial pulse instead of cutting the base current.

[0023]

According to the method of the present invention, since the means for preventing the discharge of the capacitor is inserted in the circuit through which the direct current flows, inexpensive semiconductor parts can be used and the dial pulse can be transmitted without delay. There is.

[Brief description of drawings]

FIG. 1 is a block diagram of the principle of the present invention.

FIG. 2 is an operation timing chart of the present invention.

FIG. 3 is a circuit configuration diagram of an embodiment.

FIG. 4 is a connection configuration example of a PBX office line trunk.

FIG. 5 is a circuit configuration diagram of Conventional Example 1.

FIG. 6 is an operation timing chart of Conventional Example 1.

FIG. 7 is a circuit configuration diagram of Conventional Example 2.

FIG. 8 is an operation timing chart of Conventional Example 2.

FIG. 9 is a circuit configuration diagram of Conventional Example 3.

[Explanation of symbols]

 1,13,21 Switch exchange pseudo circuit 2 Photo coupler for receiving dial signal 3,23 Transistor for sending dial pulse 4,24 Transistor for base current control 5,25 Choke circuit capacitor 6,26 Choke circuit resistor 7 Discharge prevention Photocoupler 11 Control device 12 Dial signal sending circuit 14 Electronic choke circuit with dial pulse sending function 22 Dial signal receiving circuit 31 PBX 32 Station line trunk 33 Network 34 Central control unit 35 Subscriber circuit 36 Subscriber terminal 37 Station switch 38 station line

Claims (1)

[Claims] 1. A capacitor (3) which connects a transistor (3) and a resistor (6) for biasing between the base and collector of the transistor (3) and blocks an AC component between the base and emitter of the transistor (3). In order to cut off the collector current to the transistor (3) in the computerized choke circuit with dial pulse sending function, which is connected to 5), and the local exchange pseudo circuit is connected between the collector and the emitter of the transistor (3). A photocoupler (7) having a transistor (4) for interrupting a direct current when the transistor (4) interrupts a collector current of the transistor (3). For receiving a dial signal that is provided between the connection point of the transistor and the emitter of the transistor (3) and controls the on / off of the transistor (4). Photocoupler (2) a dial pulsing function electronic choke circuit, characterized in that the the on / off operation of the discharge preventing photo-coupler (7) to be opposite to each other.