JPS6367068A - Charging pulse sending-out circuit - Google Patents

Abstract

PURPOSE:To miniaturize a circuit, and to decrease generation of a noise caused by a charging pulse, by allowing a constant-current to flow to a charging pulse sending-out circuit, and using a signal which has been allowed to pass through a filter for a voltage for controlling the constant-current. CONSTITUTION:In an incoming trunk ICT, when a charging pulse sending-out contact mp<0> operates, a (+) input of an arithmetic amplifier IC is varied gradually by a charge electric discharge of a capacitor C, and a transistor Q is set gradually to a cut-off state. When the contact mp<0> is released, the (+) input of the operational amplifier IC is varied gradually by the capacitor C in the same way, and the transistor Q becomes gradually a conducting state, therefore, the noise caused by disconnection of a loop decreases. Also, since a low-pass filter constituted of a retardation coil RET and capacitors CF0, CF1 and CF2 is provided on a speech line, generation of a noise can be prevented entirely.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a telephone switching network, and in particular to a circuit for transmitting billing pulses as a signal between outgoing trunks and incoming trunks that form communication paths between exchanges. be.

[Conventional technology]

FIG. 3 is a diagram showing a conventional connection between an outgoing trunk and an incoming trunk, and an outline of its circuit, focusing on billing pulse control. In the figure, OCT is an outgoing trunk, E is a response monitoring relay, EA is a response storage relay, and M is a billing pulse relay relay.

Also, ICT is the incoming trunk, A is the front monitoring relay%mp
' is the relay MP contact for meter pulse transmission, omitting the winding, the filter is a low-pass filter, and its component RET is the blockage wire, cotcl j'
4 is a capacitor.

Next, this operation will be explained. Activation is applied from the outgoing trunk OCT to the incoming trunk ICT, and when the called party answers, the winding is omitted and the connection status of the contacts an and at of the relay D changes, and the polarity of the power to the communication line is reversed, and the outgoing trunk OCT is activated.
Convey the called party response to the GT. In the outgoing trunk OCT, a response monitoring relay E operates, and a response storage relay EA operates and maintains its memory. In addition, outgoing trunk OCT
Relay B, whose winding is not shown, is in operation, and its contacts bo and bl are also in operation.Next, when transmitting a charging (meter) pulse, the relay MP of the incoming trunk ICT is ), the voltage (
-48V) supply is cut off. Then, as shown in FIG. 4(d), the response monitoring relay E of the outgoing trunk OCT is restored, and the billing pulse relay relay M is activated as shown in FIG. 4(d). Then, the contact mp0i of the incoming trunk ICT recovers, the relay E of the outgoing trunk OCT operates, and the relay M of the outgoing trunk OGT recovers slowly, but the contact remains silent el
Therefore, during the one hour slot of this relay M, +50V is sent from the terminal C to the frequency meter as shown in FIG. During this time, relay EA maintains its full operating state as shown in FIG. 2(C).

The above is a series of operations for transmitting a charging pulse from a response. When transmitting a charging pulse, the DC current flowing between the incoming trunk ICT and the outgoing trunk OGT is cut off.

Due to this rapid current change, the contact point mp0 generates excessive noise, so the low-pass filter consisting of a wire ring and a capacitor plays the entire role.

The pass frequency band of this filter is quite low (it needs to be set, so it is necessary to use all the inductance and capacitance that make up the filter, which have quite large values. In some cases, the filter It is necessary to have a total of two stages.

Furthermore, all capacitors used in this circuit must have a high withstand voltage, which also increases the size.

[Problem that the invention seeks to solve]

As mentioned above, in the conventional billing pulse sending circuit, the inductance (L) and capacitance (C
), it is necessary to use the full value of both of them, and of course the external dimensions are also thick.Contrary to the recent demands for miniaturization and weight reduction, which are typified by the words "light, thin, short, and small," it is necessary to downsize the charge pulse sending circuit. Furthermore, it was not possible to downsize the input trunk itself.

[Means to solve all problems]

The present invention is installed on the power supply side of a conventional communication current supply circuit that uses all blocked line loops, and instead of a relay contact for cutting off the loop current, this part is made into a constant current circuit, and furthermore, the entire line voltage is detected. The line voltage is passed through a filter circuit as a reference input to the constant current circuit, and the line voltage is connected or disconnected to the filter circuit by a line voltage total charging pulse signal.

[For production]

When the loop current is cut off or turned on, the current can be smoothly decreased and increased by the time constant of the filter.

〔Example〕

FIG. 1 is a diagram showing a first embodiment of the present invention, in which transistors Q are all connected in place of the billing pulse sending contact mp' in the incoming trunk ICT shown in FIG. 3, which shows a conventional example. . The base of this transistor Q is connected to the resistor R+t
' is connected to the output of the operational amplifier IC through the resistor Ro', and the input of the operational amplifier IC is connected to the contact mp through the resistor Ro'.
It is connected to the B line of the incoming trunk ICT via the casing break contact and further via the resistor R1. The input of the operational amplifier IC is also connected to a capacitor C, and the other terminal of the capacitor C is a contact mp'! 48 with the other side
V-, connected. On the other hand, the ←) input of the operational amplifier IC is connected to the A line side of the winding of the relay A.

As understood from the above configuration, the operational amplifier IC,
Resistor R8, transistor Q and relay A (220Ω
) constitutes a constant current circuit for controlling the total current of the primary winding resistance of relay A. Furthermore, resistor R8+RI and capacitor C form a primary filter of CR configuration.

Next, the operation of this circuit will be explained. Before the start of discharge, the (→ input is at the same potential as the ←) input of the operational amplifier IC, relay D is operating, and contacts ao,
al is in the opposite state as shown, so transistor Q is saturated.

Now, when the charging pulse sending contact mp0 operates, the voltage at the (+) input of the operational amplifier IC changes through the voltage determined by the time constant of the capacitor C and the resistor, and finally becomes -48V. Become. At this time, the input voltage of the operational amplifier IC (→input voltage) gradually changes to -48V, so the output of the operational amplifier IC is controlled by the transistor L to change the input voltage of the operational amplifier IC (→input voltage In other words, it acts to reduce the voltage on the relay's primary winding (I).This increases the emitter-collector voltage of transistor Q, causing the loop current to gradually decrease. Eventually, the transistor Q turns off and completely cuts off the L loop current.

As explained above, the voltage of the relay A (I side) of the resistor changes at the same voltage as the discharge voltage of the capacitor C, so that the generation of noise can be reduced.

When the contact mp' is restored and the loop current is applied, the (+) voltage of the operational amplifier IC is 148
The voltage rises from V to the voltage of the B line according to a time constant determined by the series resistance of the resistors and the capacitor. Therefore, even when the loop current is fully applied, the current can be gradually increased. The resistor R1 is used to adjust the time constant in order to make the charging and discharging voltage waveforms approximately the same.

In the embodiment shown in FIG. 1, in order to more completely prevent the generation of noise, the blockage wire RET and the capacitor CF6 +
A low-pass filter consisting of CFIs CFt is installed in the telephone line, but the cutoff frequency of this filter can be set much higher than that of the conventional filter shown in Figure 3, and its inductance (g The value of capacitance (C) can also be made smaller.In addition, in this embodiment, the operational amplifier IC, the transistor Q1, the resistor RQ
s ” I v R2 and capacitor C components are added, but the above paste.

The effect of being able to reduce C is significant, and the billing pulse sending circuit as a whole can be made considerably smaller.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

In the figure, IC0 is an operational amplifier, R6, R,.

R3 is a resistor, C0, C, are capacitors, and the entire active secondary low-pass filter is configured.

The amplifier, operational amplifier IC, resistor R2, transistor Q, and relay A (I side) constitute the entire constant current circuit. Although this embodiment also sends out charging pulses for the operation and recovery of the contact mpO, it is possible to make the changes in the loop current smoother than in Fig. 1, and it is possible to make the changes in the loop current smoother than in Fig. 1. No low pass filter provided. This operation can be easily understood by referring to Figure 1, so a detailed explanation will be provided (see below).

It should be noted that the blocking line RET is used to increase the impedance of the billing pulse output path and the front monitoring circuit (relay A) to the communication path.

The circuit of this embodiment requires an active secondary filter, and the circuit configuration for billing pulse sending control is somewhat complicated. Since it is not necessary, it is more effective for downsizing.

In addition, the capacitor used in the charge pulse sending control circuit (secondary active low-pass filter) has a low operating voltage and a high resistance value. Needless to say, since it can be made high, a small capacity (small size) one is sufficient.

〔Effect of the invention〕

As explained above, according to the present invention, the billing pulse sending circuit is made constant current, and the constant current control voltage is configured to use a signal sound that is passed through a filter, thereby eliminating the need to increase the size of the circuit. This has the effect of reducing the occurrence of noise when sending billing pulses due to loop break signals.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, Fig. 2 is a circuit diagram showing another embodiment of the invention, Fig. 3 is a circuit diagram showing a conventional example, and Fig. 4 is a complete circuit diagram of the present invention. The time chart shown in FIG. 5 is a circuit diagram showing another conventional example. A---- Front monitoring relay, c, co, CI, CFo
. CFl, CF2---- Capacitor, IC, ICo,
IC, --- operational amplifier, Q... transistor,
%+RI~R3...resistor, ■ZET...blockage wire.

Claims (1)

[Claims] In a billing pulse sending circuit between trunks that uses a direct current loop disconnection signal as a billing signal between exchanges, the loop current disconnection billing signal is connected to a communication line by a blocking wire and installed on the power supply side of the communication current. The circuit is configured with a constant current circuit, the line voltage detected from the billing sending line is passed through a low-pass filter as a reference input of the constant current circuit, and the line voltage is used as the reference input of the constant current circuit to send billing pulses. A billing pulse sending circuit characterized in that the circuit is connected or disconnected by a control signal.