JPS6155821B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a howler signal sending circuit for a telephone exchange.

Generally, when a subscriber forgets to take off the handset, the exchange supplies a sine wave signal with a frequency of 400 Hz that alternates between a 0.5 second transmission period and a 1 second rest period, and increases the amplitude in stages. He was giving a warning by letting him know.

This warning is called a howler signal, and the maximum level
It is a large amplitude signal of about 34 dBm (amplitude value 55 V).

Conventional telephone exchanges used mechanical contacts such as relays and crossbar switches as switch elements in the communication path circuits, making it possible to exchange not only voice signals but also large-amplitude signals such as howler signals and bell signals. It was hot.

For this reason, howler signals were normally supplied to each subscriber via a communication path circuit from a howler signal supply circuit provided on the trunk side.

On the other hand, in electronic exchanges such as space-division type exchanges in which silicon-controlled rectifiers and low-voltage semiconductor switching elements such as C/MOS are used in the communication path circuits, or time-division type exchanges in which the communication path circuits are based on the PCM and ΔM systems, There are amplitude limitations on the signals that can be exchanged, making it extremely difficult to transmit the howler signals and bell signals.

For this purpose, conventionally, a switch element is added to selectively connect the subscriber corresponding to the subscriber circuit provided between the subscriber and the switching circuit to either the Howler signal supply circuit or the switching circuit. A method was devised for sending Howler signals to each subscriber.

However, this switch element still uses mechanical contacts such as relays to open and close howler signals with large diameter amplitudes, and this is a major obstacle to making subscriber circuits smaller, lighter, and lower in power consumption. was.

Furthermore, when a howler signal is being supplied to a certain subscriber, if another subscriber is requested to send out a howler signal, the output of the howler signal supply circuit is for supplying it to the first subscriber. If the second subscriber is connected as it is, a howler signal of a suddenly high level will be sent to the second subscriber. To prevent this, (1) if necessary, install a switch matrix between the subscriber and the switching circuit to exchange with multiple Howler signal supply circuits, or (2) if the first subscriber Either the second subscriber must be kept in a waiting state while the Howler signal supply circuit is locked out and the Howler signal supply circuit becomes vacant, or the former requires an increase in the amount of hardware and costs. , the latter will lead to a decline in service.

SUMMARY OF THE INVENTION An object of the present invention is to provide a howler signal transmission circuit that is small, lightweight, low in power consumption, and economical and can be supplied to a plurality of subscribers at the same time.

According to the present invention, a counting circuit to which a clock pulse having a predetermined frequency is applied to the input and a control circuit performs start and stop control and initial setting of the clock pulse counting, and a subscriber line. A variable gain amplifier circuit having an output connected thereto and having a gain controlled according to the output of the counting circuit, and an exchange circuit having a function of connecting the input of the variable gain amplifier circuit to a Howler signal supply circuit. A howler signal transmission circuit is obtained.

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a diagram showing an example of a conventional howler signal sending circuit, in which a howler signal supply source 100 and a variable resistor 101 connected in parallel to this supply source 100 are shown.
and first and second switch elements 10 for selectively connecting the first subscriber 102 to either the communication path circuit 103 or the Howler signal supply source 100.
4, 105, and third and fourth switch elements 107, 108 for selectively connecting the second subscriber circuit 106 to either the talk path circuit 103 or the Howler signal source 100.

When it is detected that the first subscriber 102 has forgotten to take off the handset, the first subscriber 102 is connected to the Howler signal source 100 by the first and second switch elements 104, 105.

Thereafter, when the resistance value of the variable resistor 101 is increased stepwise, the first subscriber 102 is supplied with a Howler signal whose amplitude value increases stepwise.

If a subscriber is not detected to be on-hook even after a warning is given, a so-called line lockout measure is taken, in which the subscriber is separated from the subscriber monitoring by a control circuit (not shown).

When the howler signal is being supplied to the first subscriber 102, it becomes necessary to send the howler signal to the second subscriber 106, and the third and fourth switch elements 107 and 108 When connecting the subscriber 106 of to the Howler signal source 100,
This second subscriber is suddenly supplied with a high-level howler signal.

Therefore, the supply of the Howler signal to the second subscriber 106 must wait until the lock-out procedure of the first subscriber 102 is completed.

Furthermore, first and second switch elements 104,
105 and third and fourth switch elements 107,
Mechanical contacts such as relays are still used in 108 to directly open and close large-amplitude Howler signals.

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

According to FIG. 2, an embodiment of the invention includes a counting circuit 203 to which clock pulses are applied and whose clock pulse counting is controlled to start, stop, and cleared by a control circuit 202; a variable gain amplifier circuit 20 whose output is connected to the circuit and whose gain is controlled according to the output of the counting circuit;
5 and a switching circuit 200 having a function of connecting the input of the variable gain amplifier circuit 205 to a low-level Howler signal supply source 201.

In FIG. 2, when it is detected that the subscriber 204 forgets to take off the handset, the communication path circuit 200 establishes a communication path between the subscriber 204 and the Howler signal source 201.

Thereafter, the counting circuit 203 starts counting the clock pulses applied to its input according to a command from the control circuit 202, and the gain of the variable gain amplifier circuit 205 increases in accordance with the output of the counting circuit 203.

Therefore, the low-level howler signal applied to the input of the variable gain amplifier circuit 205 via the switching circuit 200 becomes a howler signal whose amplitude increases over time and is transmitted to the subscriber 204.

When it is confirmed that the subscriber 204 has hung up the handset, the control circuit 202 instructs the counting circuit 203 to stop counting, and by clearing, the gain of the variable gain amplifier circuit 205 is initialized. Revert to the value of .

In such a howler signal supply circuit according to the present invention, since the amplitude is controlled by the counting circuit 203 provided for each subscriber, the howler signal can be sent to a plurality of target subscribers.

Furthermore, since both the variable gain amplifier circuit 205 and the counting circuit 203 can be constructed from integrated circuits, the Howler signal sending circuit can be extremely small, lightweight, and consume little power.

Here, various changes can be given to the change in the amplitude of the Howler signal over time depending on the configuration of the counting circuit 203.

FIG. 3 shows a specific example of the counting circuit 203 and variable gain amplifier circuit 205 shown in FIG.

According to FIG. 3, the variable gain amplifier circuit 205 shown in FIG. 2 includes a variable gain amplifier 300 whose input is connected to the output of the switching circuit;
In-phase amplifier circuit 30 whose input is connected to the output of 00
1 and one end to the output of this in-phase amplifier circuit 301,
300Ω connected to one end of the subscriber line and the other end respectively.
A first resistor 302 having a resistance value of 300Ω, one end of which is connected to the output of an inverting amplifier circuit 303 whose input is connected to the output of the variable gain amplifier 300, and the other end of which is connected to the other end of the subscriber line. and a second resistor 304 having a resistance value.

Furthermore, according to FIG. 3, the counting circuit 203 shown in FIG. 2 includes a flip-flop circuit 305 which is set and reset by a control circuit.
A gate circuit 30 with a clock pulse having a predetermined frequency applied to one input.
6, a ring to which a clock terminal is connected to the output of this gate circuit 306, a clear terminal is connected to the output of the flip-flop circuit, and a fourth stage output terminal _Q4 is connected to the other input terminal of the gate circuit 306.・Includes a counter 307.

The variable gain amplifier 300 shown in FIG. 3 further includes an operational amplifier 308 and third, fourth, fifth, sixth, and seventh resistors 309, 310, 311,
2 and 313, and the first, second, third and fourth stage outputs Q ₁ , Q ₂ of the ring counter 307,
It is composed of first, second, third, and fourth analog switches 314, 315, 316, and 317 _, which are opened and closed by Q 3 and Q ₄ , respectively.

FIG. 4 shows a time chart for explaining the operation of FIG. 3.

Referring to FIG. 4, ring counter 307
A clock pulse 403 having a constant period is always applied to the clock terminal of the clock through a gate circuit 306. However, the output of the flip-flop circuit 305 is connected to the clear terminal of the ring counter 307, and its value is controlled to maintain the logic level L except when the howler signal is sent. Stage outputs Q ₁ , Q ₂ , Q ₃ and Q ₄ all output logic level L.

As a result, the first, second, third, and fourth analog switches 314, 315, 316, and 317 all remain open, and the variable gain amplifier 300 operates as a voltage follower circuit with a gain of 1. There is.

A control circuit (not shown) provides a flip-flop signal.
When the set pulse 400 arrives at the set terminal of the flop circuit 305, it causes the flip
The output of the flop circuit 305 rises to a logic level H, as shown at 402 in FIG.

Upon receiving this output, the ring counter 307 starts counting the clock pulses 403, and as shown in _FIG . stand up.

This causes the first analog switch 314
When the variable gain amplifier circuit 300 is closed, the variable gain amplifier circuit 300 functions as an in-phase amplifier circuit whose gain is determined by the resistance value of the third resistor 309 and the resistance value of the fourth resistor 310.

The following clock pulses 403 are added one after another.
Accordingly, the logic level H of the first stage output _Q1 is the fourth
As shown in FIGS. 405, 406 and 407, the output is sequentially shifted to the second stage output Q ₂ , the third stage output Q ₃ and the fourth stage output Q ₄ .

As a result, the on state of the first analog switch 314 also shifts to the second analog switch 315, the third analog switch 316, and the fourth analog switch 317, so that the gain of the variable gain amplifier 300 also changes. The resistance values of the fourth resistor 310, the fifth resistor 311, the sixth resistor 312, and the seventh resistor 313 change in a stepwise manner.

Finally, when the fourth stage output _Q4 rises to logic level H, this closes the gate circuit 306, so no clock pulse 403 arrives at the clock terminal of the ring counter 307, and the fourth stage Output _Q4 continues to maintain logic level H.

As a result, the gain of the variable gain amplifier circuit 300 continues to maintain the value determined by the resistance value of the third resistor 309 and the resistance value of the seventh resistor 313.

In this way, the low-level howler signal supplied to each subscriber circuit via the exchange circuit is converted by the variable gain amplifier 300 into a large-amplitude howler signal whose amplitude changes stepwise over time, and then Amplification circuit 301 and inverting amplification circuit 30
3 into a ground-balanced howler signal and then supplied to the subscriber through first and second resistors 302 and 304.

When a reset pulse 401 is applied from the control circuit, the output of the flip-flop circuit 305 falls to the logic level L as shown in FIG _. Q ₂ , Q ₃ , Q ₄ are also shown in Figure 4 404, 405,
As shown at 406 and 407, it falls to logic level L.

Accordingly, the first, second, third, and fourth analog switches 314, 315, 316, and 317 are all opened, and the variable gain amplifier circuit 300 again functions as a voltage follower with a gain of 1. Used to transmit audio signals.

In the specific example of FIG. 3, a ring counter 307 is used for the counting circuit 203 of FIG. 2, but this can also be configured with a binary counter and a decoder.

Furthermore, a binary counter is used in the counting circuit 203 in FIG. analog switch 31
A similar Howler signal sending circuit can be obtained by configuring the circuit network of 4, 315, 316, and 317 to be a power of 2.

As described above, by using the present invention, it is possible to obtain a howler signal transmission circuit that is small, lightweight, low in power consumption, and economical and can be supplied to a plurality of subscribers at the same time.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional howler signal sending circuit, FIG. 2 is a diagram showing a howler signal sending circuit according to the present invention, FIG. 3 is a diagram showing a specific example of the howler signal sending circuit according to the present invention, and FIG. 3 is a diagram showing a time chart for explaining FIG. 3. FIG. In the figure, 100 and 201 are Howler signal sources, 103 and 200 are communication path circuits, and 104 and 1
05, 107 and 108 are switch elements, 20
2 is a control circuit, 203 is a counting circuit, 205 is a variable gain amplifier circuit, 301 is an in-phase amplifier circuit, 303 is an inverting amplifier circuit, 308 is an operational amplifier, 306 is a gate circuit, and 307 is a ring counter.

Claims (1)

[Claims] 1 a counting circuit to which a clock pulse having a predetermined frequency is applied to an input and a control circuit performs start and stop control and initial setting of the clock pulse counting; A howler signal comprising: a variable gain amplifier circuit whose gain is controlled according to the output of a counting circuit; and an exchange circuit having a function of connecting the input of the variable gain amplifier circuit to a howler signal supply circuit. Sending circuit.