JPH0329348B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a circuit for controlling the receiving state of a public telephone of the first loop type.

[Prior art]

Generally, in front-loop public telephones,
Since the DC loop circuit is closed only by the off-hook, the telephone circuit is bypassed to disable transmission and reception, and the state in which transmission and reception are disabled is canceled when a coin is inserted. In the case of a central power system, where control is performed by the power supply of the exchange via The incoming howler sound is emitted from the handset to warn you to remove the handset.

However, depending on the type of exchange, if the off-hook state continues, the power supply to the telephone line may be automatically cut off. If this is not done, the handset will not ring even if the howler sound is transmitted from the telephone side, resulting in the disadvantage that it is impossible to warn that the handset has been removed.

[Summary of the invention]

The purpose of the present invention is to fundamentally solve such drawbacks of the conventional art, and to provide a central power supply-operated front-loop type public telephone that is normally disabled for receiving calls and releases the disabled state by inserting a coin. The circuit includes a switch that is inserted into the loop circuit and is always on, a control section that turns off the switch only when the central office exchange does not recover if no normal operation is performed within a certain period of time after off-hook, and a recovery system. A release relay is provided which is connected in parallel to the switch, and when the switch is turned off, a loop current flows to maintain the operation, and when the switch is turned off, the inability to receive calls is released, and the release relay is restored in response to the on-hook. It is something that

〔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 in 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 _. 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 constant voltage diode ZD ₁ inserted in the direction generates a Zener voltage with respect to the loop current with the line terminal L ₁ as the positive terminal. The Zener voltage charges the capacitor C ₁ through the reverse blocking diode D ₁ ,
The control unit CNT performs control operations in response to this terminal voltage being supplied as a local power supply.

However, for the communication circuit TKC, a chain circuit consisting of contact ss ¹ of a magnetic latching type blocking relay SS and contact sh ¹ of a similar release relay SH is connected in parallel, and initially these were connected to each other in parallel. Since the break terminals are connected to each other, making it impossible to send and receive calls, it is impossible to make calls using only the off-hook. However, the coin detection circuit CCD, which includes a photoelectric detector, etc., is placed in the curing storage mechanism, which is omitted from the diagram.
According to the detection force of the blocking relay SS, the operating winding F
If you drive, the same relay SS will maintain operation,
Sending and receiving calls is possible by operating contact SS ¹ , and the call circuit changes depending on the operation of the dial circuit DIC.
A dial call is made as the switching element in the TKC turns on and off. Note that in the above embodiment, contacts ss ¹ and sh ¹ are connected to the communication circuit.
It is connected in parallel to TKC, and when it is on, it shorts the communication circuit TKC and disables transmission and reception.
The handset in the communication circuit TKC may be short-circuited to disable only receiving calls.

In addition, the recovery winding R of the blocking relay SS is driven in response to the turning on of the switch HS ² due to the on-hook, while the charge in the capacitor C ₁ is not discharged, and thereby the recovery of the relay SS is performed. It is becoming.

In contrast to the above, the detection power of the curing detection circuit CCD is not generated during a certain period of time after off-hook, or
If the dial circuit DIC does not generate an output and normal operations such as coin insertion or dialing are not performed, the control unit CNT determines this using a timer that starts according to the local power supply and controls the operation of the blocking relay SS. Without doing so, the switch SW is controlled while the call is disabled, and it is turned off for a period of time (for example, several tens of milliseconds) until the central office is restored, thereby opening the DC loop circuit.

Then, in response to the switch SW being turned off, a loop current flows through its own transfer contacts sh ² and sh ³ to the release relay SH connected in parallel with the switch SW, which maintains the operation, so that the contact sh ¹ operates. This disconnects the interconnection with contact SS ¹ , cancels the call-disabled state, and when a howler sound arrives, this is the switch SW and voltage regulator diode.
It passes through ZD ₁ and is applied to the communication circuit TKC, causing the receiver to ring.

On the other hand, a recovery route for the release relay SH is prepared by contacts sh ² and sh ³ , and if the on-hook is performed in response to the howler sound of the receiver, line terminal L ₁ - hook switch HS ¹ - contact sh ³ - release Relay SH - Contact sh ² - Diode D ₂ - Line terminal L ₂
Through this route, the half-wave component of the howler sound travels in the opposite direction to that during operation, thereby restoring the release relay SH and returning to its initial state.

Therefore, if the switch is left off-hook and the switch SW is turned off before the exchanger disconnects the power supply, and the release relay SH maintains its operation, even if the power supply from the exchanger is disconnected, The receiver can be made to ring in response to the howler sound.

The control unit CNT also monitors the dialed number and coin storage status, and if it determines that a prohibited number or coin storage is incorrect, it turns off the switch SW accordingly and sends the exchanger a recovery. At this time as well, the make poles of contacts ss ¹ and sh ¹ are connected to each other in order to disable communication by maintaining the operation of release relay SH.

In addition, contacts sh ₂ and sh ³ are of early make type.
(E) Using a circle, the break pole is turned off after the release relay SH sufficiently approaches the operation holding state, and the make pole is turned off after the release relay SH sufficiently approaches the recovery state. is necessary.

In addition, the connection parts of contacts ss ¹ and sh ¹ should be at least parts that can disable reception, and the same applies even if the operation and recovery of each relay SS and SH are reversed. Even if the control operation of the CNT is stopped, if the configuration allows howler sound to pass through, circuits made of various semiconductor elements can be used, and if the circuit remains turned off even in response to howler sound. , Switch SW
It is sufficient to provide a condenser for the side passage.

In addition to the relays SS and SH that maintain operation using permanent magnets, relays that maintain operation mechanically may also be used, and the control unit CNT may be equipped with various types of logic without using a processor. Various modifications are possible, such as using a dedicated circuit constructed by combining circuits.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, even in an exchange that automatically cuts off power supply to a telephone line in response to continued off-hook, if no regular operation is performed within a certain period of time after off-hook, The inability to receive calls is automatically released, and the howler sound ensures that the handset rings, providing a remarkable effect in various types of public telephones using the forward loop system.

[Brief explanation of the drawing]

The figure is a circuit diagram showing an embodiment of the present invention. L ₁ , ₂ ...Line terminal, HS ¹ , HS ² ...Hook switch, TKC...Talking circuit, SW...Switch, D ₁ , D ₂
…diode, ZD ₁ …constant voltage diode, CNT
…control unit, SH…release relay, SS…blocking relay,
ss ¹ , sh ¹ ~ ^{sh 3} ...Contacts.

Claims (1)

[Scope of Claims] 1. In a telephone receiving control circuit of a central power-operated front-loop type public telephone that is always disabled for receiving calls and released by inserting a coin, the telephone is inserted into the loop circuit and is always on. a control unit that turns off the switch for a period when the central office exchange is not restored when no normal operation is performed within a certain period of time after off-hook; A public telephone set comprising: a release relay that maintains operation by causing a loop current to flow when the telephone is turned off, releases the inability to receive a call by holding the operation, and restores the state in response to an on-hook state. Receiving control circuit.