JPS6411190B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reminder signal transmission control device for controlling the transmission of a reminder signal in a public telephone according to the type of call.

For types of calls made on public telephones, a charging signal arrives only once when the called party answers, and the charge for one call (in coins or credits) is collected, and after that, no charging signal arrives and the time is unlimited. There are unlimited short-distance calls that can be made to. This unlimited short-distance call requires only the fee for one call, so there is no need to send a reminder signal.

However, as shown in FIG. 1, the conventional reminder signal sending control device 1 includes a billing signal receiving circuit 3 which outputs a billing signal detection signal upon receiving a billing signal coming from an exchange 2, and a billing signal receiving circuit 3 which receives the billing signal detection signal. Then, the remaining input amount (coins or credits) is compared with the call fee for one call, and if there is no remaining amount for one call or more, a reminder signal sending circuit 4 is configured to send out a reminder signal. For this reason, even though a reminder signal is not required in the case of the above-mentioned unlimited short-distance call, one billing signal arrives after the called party answers, and the remaining amount after collecting the charge for one call is charged per call. There was a drawback that a reminder signal would be sent out if the rate fell below the current rate. (In Figure 1, 5 is a public telephone, 6 is a telephone circuit, 7a is a telephone line, 7
b is the ground, and L1 and L2 are line terminals. ) For this purpose, a method may be considered in which it is detected whether or not the number of times the charging signal arrives is two or more times, and if the number of times the charging signal arrives is only once, the reminder signal is not sent. However, with this method, it is not possible to determine whether or not it is an unrestricted short-distance call when the first charging signal arrives, so a reminder signal cannot be sent in response to the first charging signal even if the call is not an unlimited short-distance call. There is.

The object of the present invention is to provide a reminder signal sending control device for a public telephone set that overcomes these drawbacks.

An embodiment of the present invention will be described below based on the drawings.

FIG. 2 shows a block diagram of a reminder signal sending control device for a public telephone set according to the present invention, in which the same components as in FIG. 1 are given the same reference numerals and the details thereof are omitted.

The reminder signal sending control device 11 according to the present invention includes:
Signal receiving circuit 12 and line polarity detection circuit 13
, an identification circuit 14 , a gate circuit 15 , and a reminder signal sending circuit 16 .

When the signal receiving circuit 12 receives a billing signal or a signal equivalent to a billing signal transmitted between the telephone line 7a of the public telephone 5 or between the telephone line 7a and the earth 7b from the exchange 2, it outputs a reception signal. Here, the signal equivalent to the billing signal identifies whether or not it is a long-distance call based on a dial signal sent from the public telephone 5 to the exchange 2 in the exchange 2. In the case of a long-distance call, the called party This is a signal sent from the exchange 2 to the telephone line 7a of the public telephone 5 or between the telephone line 7a and the ground 7b before answering, and this signal is composed of a signal having the same frequency as the billing signal.

In the public telephone 5, the line polarity of the call line 7a is such that line terminal L1 has + polarity and line terminal L2 has - polarity, and after the called party answers, line terminal L1 changes to -.
The line terminal L2 is configured to reverse polarity to + polarity, and the line polarity detection circuit 13 outputs a polarity reversal detection signal when detecting this polarity reversal.

When the identification circuit 14 receives the received signal from the signal receiving circuit 12 before the line polarity change (that is, before the line polarity detection circuit 13 outputs the polarity change detection signal), the identification circuit 14 stores it and sends it to the reminder signal sending circuit 16. It is designed to output an identification signal indicating a distance call. That is, the identification circuit 14 has the role of detecting whether or not a signal equivalent to a billing signal is sent from the exchange 2 before the called party responds, and if so, identifying that it is a long-distance call. .

When the gate circuit 15 receives the received signal from the signal receiving circuit 12 after the line polarity is reversed (that is, after the line polarity detection circuit 13 outputs the polarity reversal detection signal), it passes this received signal. That is, the gate circuit 15 passes only the received signal that the signal receiving circuit 12 receives and outputs the billing signal after the polarity change, and passes the received signal that the signal receiving circuit 12 receives and outputs the billing signal equivalent signal before the polarity change. is not allowed to pass through.

Only when receiving the identification signal from the identification circuit 14, the reminder signal sending circuit 16 passes through the gate circuit 15 and receives the reception signal from the signal receiving circuit 12, and then the remaining input amount is equal to one call. It is designed to send a reminder signal if the price falls below the toll.

Next, the operation of the public telephone reminder signal sending control device configured as described above will be explained.

In the case of a long-distance call using a dial signal from the public telephone 5, a signal equivalent to a billing signal indicating a long-distance call arrives from the exchange 2 between the call line 7a or between the call line 7a and the ground 7b before the called party answers. do. When the signal receiving circuit 12 receives this signal equivalent to the billing signal, it outputs the received signal to the identification circuit 14 and the gate circuit 15. Since there is no polarity reversal before the called party responds, no polarity reversal detection signal is output from the line polarity detection circuit 13. Therefore, the identification circuit 14 outputs an identification signal to the reminder signal sending circuit 16. Further, the received signal is blocked by the gate circuit 15 and is not output to the reminder signal sending circuit 16.

Next, when the called party answers, the polarity of the telephone line 7a is reversed, and the line polarity detection circuit 13 outputs a polarity reversal detection signal. When a billing signal arrives from the exchange 2 after polarity reversal, the signal receiving circuit 12 outputs a received signal. Since the polarity reversal detection signal is output from the line polarity detection circuit 13 to the gate circuit 15,
The received signal passes through a gate circuit 15 and is input to a reminder signal sending circuit 16. At the time of this input, if the remaining amount is less than one call, a reminder signal is sent out from the reminder signal sending circuit 16.

In the case of an unrestricted short-distance call, a signal equivalent to a billing signal before the polarity change does not arrive, so no reception signal is output from the receiving circuit 12 before the polarity change. Therefore, since the identification signal is not output from the identification circuit 14,
Even if the received signal from the signal receiving circuit 12 passes through the gate circuit 15 and is input to the prompting signal sending circuit 16 due to the arrival of the first billing signal after the polarity change, no prompting signal is sent out. In this way, in this reminder signal transmission control device, before the called party responds, the identification circuit 14 identifies whether the call is a long distance call or an unlimited short distance call, and the reminder signal transmission circuit 16
It is designed to decide whether or not to send out a reminder signal when a billing signal arrives.

FIG. 3 shows a specific circuit example of the reminder signal sending control device shown in the block diagram in FIG.

The line polarity detection circuit 13 includes a photocoupler 17 for detecting polarity, a diode 18 connected in the opposite direction to the photodiode of the photocoupler 17, and a resistor 19 connected to the collector of the output transistor of the photocoupler 17. , the emitter of the phototransistor is grounded, and the collector is connected to the voltage V via a resistor 19.

The identification circuit 14 is composed of an AND circuit 20 and a flip-flop 21, and the gate circuit 15 is composed of an inverter 22 and an AND circuit 23.

In the case of a long-distance call, a signal equivalent to a billing signal is received before the polarity change, and a received signal "1" is input from the signal receiving circuit 12 to the AND circuits 20 and 23. Before the called party answers, line terminal L1 has + polarity and L2 has - polarity.
Because of the polarity, the line current flows through diode 18 and the output transistor of photocoupler 17 does not conduct. Therefore, a signal "1" is output from the line polarity detection circuit 13. Therefore, the output signal "1" of the AND circuit 20 is input to the flip-flop 21. Therefore, the identification signal "1" is output from the output terminal Q of the flip-flop 21 to the reminder signal sending circuit 16. On the other hand, in the AND circuit 23, since the output of the inverter 22 is "0", the output of the AND circuit 23 is "0".

After the called party answers, the polarity is reversed and the line terminal L1
has negative polarity and L2 has positive polarity. For this reason, the output transistor of the photocoupler 17 becomes conductive, so
The output of the line polarity detection circuit 12 becomes "0".
After the polarity change, the charging signal is received and the signal receiving circuit 12
The received signal is input to the AND circuit 20, but since the output of the line polarity detection circuit 12 has become "0", the output of the AND circuit 20 will remain "0" thereafter. Therefore, the state of the Q output of flip-flop 21 does not change and is held at "1". on the other hand,
The output of the inverter 22 of the gate circuit 15 is “1”
Therefore, when the received signal "1" is input to the AND circuit 23, the output of the AND circuit 23 becomes "1". Therefore, the signal “1” from the AND circuit 23
is input to the reminder signal sending circuit 16. At this time, if the remaining amount is less than one call, a reminder signal is sent out from the reminder signal sending circuit 16.

In the case of an unlimited short-distance call, the signal receiving circuit 12 does not output a received signal "1" before the polarity change.
Therefore, the Q output of flip-flop 21 is "0". After polarity reversal, even if the received signal “1” is input to the AND circuit 20, the line polarity detection circuit 13
Since the output of the flip-flop 21 is "0", the Q output of the flip-flop 21 is held as "0". For this reason,
When the billing signal arrives after the polarity change, the reception signal "1" is input to the AND circuit 23, and even if the output of the AND circuit 23 becomes "1", no reminder signal is sent out.

As the line polarity detection circuit 13, as shown in FIG. 4, a photocoupler 17 and a diode 18 may be connected in the opposite direction to those shown in FIG. 3, and a resistor 19 may be connected between the emitter of the phototransistor and ground. In this configuration, before the called party responds, the line terminal L1 has a positive polarity and the line terminal L2 has a negative polarity, so the output transistor of the photocoupler 17 is conductive. Therefore, line polarity detection circuit 1
The output of 3 becomes "1". After the polarity is reversed, the output transistor is not conductive, so the output of the line polarity detection circuit 13 becomes "0". In this way, the same result can be obtained with the configuration shown in FIG.

However, in the configuration shown in FIG. 4, if dialing is a method in which the line current is intermittent, the output transistor is turned OFF every time the line current is momentarily cut off when the dial impulse is sent before polarity change. Therefore, a capacitor 24 is added to form a delay circuit with the resistor 19 and the capacitor 24, and by setting the time constant of this delay circuit to be longer than the dial impulse, the output is kept at "1". This prevents it from being affected by dial impulses.

Note that due to trouble in the exchange 2, there may be a case where the polarity is not changed after the called party answers. FIG. 5 is designed to deal with this case as well.

That is, the identification circuit 14 is composed of a NAND circuit 25 and a flip-flop 21, and the gate circuit 1
5 is composed of a NAND circuit 26 and an AND circuit 23.

In the case of a long distance call, a received signal "1" is input to the NAND circuit 25 before the called party responds. Since the output of the line polarity detection circuit 13 is also "1", the output of the NAND circuit 25 becomes "0", thereby the Q output of the flip-flop 21 becomes the identification signal "1", and the output becomes "0". Become. If the polarity does not change after the called party responds, the output of the line polarity detection circuit 13 remains "1", and therefore the signal reception circuit 1
The output of the NAND circuit 25 becomes "0" every time the received signal "1" from the flip-flop 21 arrives, but since the D input of the flip-flop 21 is V (constant voltage), the Q,
The state of the Q output does not change.

Therefore, in the case of a long distance call, since "0" is always output from the output terminal of the flip-flop 21, the output of the NAND circuit 26 is independent of the output of the line polarity detection circuit 13 (regardless of the presence or absence of polarity reversal). ) is always “1”. Therefore, since the output "1" of the NAND circuit 25 is always input to one side of the AND circuit 23, the received signal "1" from the signal receiving circuit 12 due to the arrival of the charging signal after the called party responds to the AND circuit 23. , the output “1” of the AND circuit 23 is input to the reminder signal sending circuit 16. Therefore, there is no problem in operation even if the polarity is not reversed.

It goes without saying that not only the above-mentioned photocoupler but also a relay or the like can be used as means for detecting the line polarity.

In the public telephone reminder signal sending control device according to the present invention, before the called party answers, only in the case of a long-distance call, the signal sent from the exchange is used to identify whether or not it is an unlimited short-distance call, and the reminder signal is sent out. As a result, in the case of unlimited short-distance calls, where you can make unlimited calls for the fee for one call, you no longer have to worry about reminder signals as in the past, and in the case of long-distance calls, A reminder signal can be sent from the time the first billing signal arrives. If the fee structure differs between short-distance calls and long-distance calls,
The output signal of the identification circuit can also be used to switch the rate system.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional example, Fig. 2 is a block diagram showing an embodiment of the present invention, Fig. 3 is an embodiment showing its specific configuration, and Figs. It is a figure showing an example. 5...Public phone, 6...Telephone circuit, 7a...
Call line, 7b... Earth, 11... Reminder signal sending control device, 12... Signal receiving circuit, 13...
Line polarity detection circuit, 14...Identification circuit, 15...
...Gate circuit, 16...Reminding signal sending circuit, L
1, L2...Line terminal.

Claims (1)

[Claims] 1. A signal receiving circuit that outputs a received signal upon receiving a billing signal arriving from the exchange or a signal equivalent to a billing signal arriving from the exchange before the called party responds in the case of a long-distance call; a line polarity detection circuit that outputs a polarity reversal detection signal when detecting polarity reversal; an identification circuit that outputs an identification signal when receiving the received signal before outputting the polarity reversal detection signal; and a line polarity detection circuit that outputs an identification signal after receiving the polarity reversal detection signal; A public telephone comprising: a gate circuit that passes the received signal when receiving the signal; and a reminder signal sending circuit that sends a reminder signal when receiving the received signal from the gate circuit only when the identification signal is received. Reminder signal sending control device.