JPH0325069B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a system for controlling calls in a public telephone according to a dialed number to be called.

[Prior art]

Public telephones use various call control methods depending on the type of phone, but they monitor the dialed numbers that are generally dialed, and allow calls to be made free of charge if they are a specific number for emergency calls, but if there is a charge, However, if the number is prohibited to a toll number, calls will be blocked.

For this reason, conventionally, when a prohibited number or an unauthorized number that results in an unauthorized call is made, a method has been adopted in which the DC loop is opened for a certain period of time to restore the exchange and make it impossible to make or receive calls.

However, with such methods, the user will be left with no sound when calling a prohibited number or an illegal number, so if the user is unable to make a call due to calling a prohibited number, or when calling an illegal number. It is unclear whether a similar situation occurred due to this, and it has caused disadvantages such as undesirables.

[Summary of the invention]

The purpose of the present invention is to fundamentally solve the above-mentioned drawbacks of the conventional technology, and it makes it impossible to make a call when the dialed number to be called is a prohibited number that should be prohibited. At the same time, the DC loop circuit is forcibly opened for a certain period of time, and voice reception from the telephone line is disabled, and audible sounds generated by a built-in oscillator are sent to the receiver.

〔Example〕

Hereinafter, details of the present invention will be explained with reference to circuit diagrams illustrating embodiments.

In the same figure, a switch SW consisting of a switch HS ¹ and a switching element such as a transistor is inserted into a loop circuit between a line terminal L ₁ to which a telephone line is connected and one end of a communication circuit TKC, and a switch SW consisting of a switching element such as a transistor is inserted into a loop circuit between a line terminal L 1 to which a telephone line is connected and _one end of a communication circuit TKC. A constant voltage diode ZD ₁ is inserted between this terminal and the other end of the communication circuit TKC.

For this reason, a DC loop circuit is closed in response to the off-hook, and a loop current is passed through these, and the zener voltage of the constant voltage diode ZD ₁ inserted in the direction that generates a zener voltage with respect to the loop current with the line terminal L ₁ as the positive pole. The capacitor _C1 is charged by the voltage via the reverse current blocking diode _D1 , and the control unit CNT performs control operations in response to these terminal voltages being supplied as a local power source.

However, contact ss ¹ of a magnetic latching type bypass relay SS is connected in parallel to the communication circuit TKC, and a similar blocking relay is connected to the transmitter T of the communication circuit TKC. Since the TS contacts ts ¹ are connected in parallel, making it impossible to send or receive calls, it is not possible to make calls using off-hook alone, and the control unit CNT, which consists of a microprocessor, memory, etc. , each relay SS,
By driving the operation winding F of TS, each relay SS,
SH maintains operation and contacts SS ¹ and TS ¹ turn off, making it possible to send and receive calls, and the keyboard
In response to the control of the dial circuit DIC that responds to the operation of the KB, the switching element in the call circuit TKC turns on,
In accordance with turning off, dialing is performed.

In addition, the recovery winding R of each relay SS, TS is driven while the charge of the capacitor _C1 is not discharged in response to the turning on of the switch switch HS ² due to the on-hook, and thereby the recovery winding of each relay SS, TS is activated. It has become common practice to do so.

On the other hand, the control unit CNT is directly given the output of the keyboard KB, and when a dial call is made, the control unit CNT monitors the dialed number and prohibits calls to toll relay stations, etc. The system determines whether the number is a prohibited number, or whether the number is a four-digit number similar to a specific number that allows free calls, resulting in an unauthorized call, and then controls are carried out according to the results.

That is, the control unit CNT controls the coin detection circuit CCD.
Depending on the detection power of
Restoration control is performed only on the TS, and its contact points
By ts ¹ , the transmitter T is bypassed and transmission is disabled.

If it is determined that the number is an unauthorized number, it controls the switch SW, turns it off for 1 second, forcibly opens the DC loop circuit for a certain period of time, performs recovery control on the bypass relay SS, and closes the contact SS ¹ .
In addition to disabling transmission and reception, the built-in oscillator OSC, which is operated by the local power supply, is controlled, causing it to oscillate and generate an audible signal equivalent to, for example, a busy tone.The output is sent to the matching transformer MT and capacitor C. ₂ to the handset R of the communication circuit TKC. Since the contact ss ¹ of the receiver R is on, the voice from the telephone line is not received, and the audible sound signal from the oscillator OSC is opened.

In the above embodiment, when it is determined that the number is an unauthorized number, the relay contact ss ¹ connected in parallel to the call circuit TKC is turned on to disable sending and receiving calls, but the circuit to the handset R is cut off by a relay contact, etc. You may also disable only receiving calls.

Furthermore, based on the detection power of the coin detection circuit CCD,
If the control unit CNT determines that the coins are not properly stored or that there are no coins to be stored during a call, the same control as described above is performed.

Therefore, if you make a mistake in calling a prohibited number to a toll relay stand, etc., you will be unable to listen to the other party's calls, and you may be able to send a fraudulent number due to unauthorized operation, or your coins may be misplaced. If something like this occurs, an audible sound from the built-in oscillator OSC will be heard, allowing the user to immediately determine the cause of the call failure, and allowing emergency calls to specific numbers to be made free of charge. Become something.

However, for each relay SS and TS, in addition to the type that maintains operation using a permanent magnet, it is also possible to use a type that maintains operation mechanically, and depending on the situation, the contact
The same effect can be achieved even if break contacts or transfer contacts are used for ss ¹ and ts ¹ , and the operation and recovery of each relay SS and TS may be in an opposite relationship, and the contacts ss ¹ and ts
The connection portion of ts ¹ may be at least a portion that makes it impossible to receive calls from the telephone line, and a portion that makes it impossible to send calls and does not interfere with the closing of the DC loop circuit.

In addition, the control unit CNT does not use a particular processor, but instead uses a combination of various logic circuits.
CNT may be configured and the dial circuit DIC is
Not only one that sends out a pulse signal, but also one that sends out an audio frequency signal as a dial signal may be used.

Note that if the output of the keyboard KB is given to the control unit CNT and the dial circuit DIC, the number of output ports of the control unit CNT can be reduced. After this, the output of a plurality of bits may be sent to the dial circuit DIC, and the present invention can be modified in various ways.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, control is performed according to the dialed number to be dialed, and calls based on erroneous or unauthorized operations are completely prevented, and when a prohibited number is dialed due to erroneous operation, the call is transmitted. When a call is made to an unauthorized number due to unauthorized operation, the DC loop is opened, making it impossible to receive the call and an audible sound is heard, making it easy to distinguish between erroneous operation and unauthorized operation. Effects can be obtained.

[Brief explanation of the drawing]

The figure is a circuit diagram showing an embodiment of the present invention. L ₁ , L ₂ ... Line terminal, HS ¹ , HS ² ... Hook switch, SW ... Switch, TKC ... Telephone circuit,
T...Telephone, R...Telephone receiver, ZD ₁ ... Constant voltage diode, _D1 ...Diode, _C1 , _C2 ...Capacitor, CNT...Control unit, DIC...Dial circuit, KB... Keyboard, MT...matching transformer,
OSC: Oscillator, SS: Side path relay, TS: Blocking relay, ss ¹ , ts ¹ : Contact.

Claims (1)

[Scope of Claims] 1. In a call control system for public telephones that monitors dialed numbers and performs predetermined call control according to the dialed numbers, if the dialed number is a prohibited number that should be prohibited, the outgoing call is stopped. If the dialed number is an invalid number that would result in an unauthorized call, the DC loop circuit is forcibly opened for a certain period of time, voice reception from the telephone line is disabled, and the audible tone generated by the built-in oscillator is emitted from the receiver. Send to. A call control method for public telephones characterized by the following.