JPS6112162A - Reception control circuit of public telephone set - Google Patents

Abstract

PURPOSE:To attain howling operation by releasing disable reception when a normal operation is not executed during a prescribed time after hook-off in a public telephone set of the advanced loop system to ring a receiver. CONSTITUTION:When no detected output of a coin detection circuit CCD is caused during a prescribed time after off-hook, no output of a dial circuit DIC is caused, and no normal operation for dialing is performed, then a control section CNT does not control the operation to a block relay SS, a switch SW is controlled to open a DC loop circuit. Since a loop current flowing to a release relay SH is given in response to the off-state of the switch SW, the disabled state of talking is released and a receiver is rung when a howler tone reaches.

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, the DC loop circuit is closed only by off-hook, so the telephone circuit is bypassed to disable transmission and reception, and when a coin is inserted, transmission and reception are disabled. However, in the case of a central power supply system that uses the switchboard's power supply via the telephone line to perform off-hook operation, if the user goes off-hook intentionally or negligently, it is necessary to detect this. After canceling the disabled state, a howler sound sent from the exchange is emitted from the handset to warn the user to disconnect 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 a Howler sound is sent from the exchange, resulting in the disadvantage that it is impossible to warn that the handset has been disconnected.

[Summary of the invention]

The present invention has the purpose of fundamentally solving the drawbacks of the prior art, and includes a switch inserted into the loop circuit, so that when a normal operation is not performed within a certain period of time after off-hook, the control section is activated. To provide an extremely effective telephone answering system for public telephones, in which the switch is turned off, the release relay is held in operation in response to this, and at least the state in which it is impossible to receive a call is released, and the release relay is restored in response to on-hook. It provides a control circuit.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to circuit diagrams showing embodiments.

In the figure, a hook switch H8 and a switch SW consisting of a switching element such as a transistor are inserted into the loop circuit between the line terminal L1 to which the telephone line is connected and one end of the communication circuit TKO, and a switch SW consisting of a switching element such as a transistor is inserted into the loop circuit between the line terminal L1 to which the telephone line is connected and one end of the communication circuit TKO. A constant voltage diode zDl is inserted between the other end of the circuit TKO.

For this reason, the DC loop circuit is closed in response to off-hook, and a loose current is passed through these, and the zener voltage of the constant voltage diode ZDI inserted in the direction that generates a zener voltage with respect to the loop current with the positive polarity at the line terminal L1. In addition, the capacitor CI is charged via the reverse current blocking diode D1, and the terminal voltage of the capacitor CI is supplied as a local power supply, so that the control unit CNT performs control operations.

However, for the communication circuit TKO, a chain circuit consisting of contact IIs of a magnetic latching type blocking relay SS and contact 8h of a similar release relay SH is connected in parallel; Since the break terminals are connected to each other, making it impossible to send and receive calls, it is not possible to make calls only by off-hook. However, there is a coin detection circuit COD including a photoelectric detector etc. arranged in the coin storage mechanism omitted in the figure.
If the operating winding F of the blocking relay SS is driven according to the detected force, the relay SS will not maintain its operation.
When the dial circuit DIC is operated, the switching element in the telephone call circuit TKC is turned on and off in response to the operation of the dial circuit DIC, thereby making a dial call.

The recovery winding R of the blocking relay SS is driven in response to the on-hook turning on of the hook switch H8, while the charge in the capacitor CI is not discharged, thereby restoring the relay SS. There is.

In contrast to the above, the detection force of the coin detection circuit COD is not generated during a certain period of time after off-hook, or the dial circuit D
If no output is generated from the IC and normal operations such as inserting a coin or making a dial call are not performed, the control unit CNT uses a timer that starts in response to the local power supply to determine this and control the operation of the blocking relay SS. Instead, the switching is controlled while communication is disabled, and this is turned off for, for example, several tens of meters (8) to open the DC loop circuit.

Then, in response to the OFF of the switch SW, a loop current flows through its own transfer contacts sh and ah'i to the release relay SH connected in parallel with the switch SW, and this maintains the operation, so by the operation of the contact sh, Contact 8
11. If the interconnection with
and the constant voltage diode zD1, and the communication circuit TK
When applied to O, the handset rings.

On the other hand, a recovery route for the release relay SH is prepared through contacts sh'' and ah3, and if the on-hook is performed in response to the howler ringing of the receiver, line terminal L!-
The half-wave component of the buzzing sound passes through the route of hook switch H8 - contact 8h - release relay SH - contact 5h2 - diode D2 - line terminal L2 in the opposite direction to that during operation, and this restores release relay 8H. , becomes the initial state.

Therefore, if the switch is left off-hook and the switch SW is turned off before the switch disconnects the power supply and the release relay SR maintains its operation, the howler sound will be heard even if the power supply from the switch is cut off. The handset can be made to ring in response to the call.

The control unit CNT also monitors the dialed number and the coin storage status, and if it determines that there is a prohibited number or a coin storage failure, it switches on the switch SW accordingly.
is turned off and the exchange is restored.At this time, the make terminals of contacts ss and sh are connected to each other in order to disable communication by maintaining the operation of release relay SH.

In addition, the contacts sh and sh are early make type (E).
? It is necessary to use one in which the break pole does not turn off after the release relay SH sufficiently approaches the operation holding state, and the make pole turns off after the release relay SH sufficiently approaches the recovery state. It is.

In addition, the connection parts of the contacts as and sh may be any part that can at least disable reception, and each relay 88. S
The same is true even if the operation and recovery of H are reversed.As long as the switch SW has a configuration that allows howler sound to pass even if the control unit CNT stops the control operation, circuits using various semiconductor elements can be used. A capacitor for bypass may be provided to the switch SW as long as it can be used and remains off even in the presence of noise.

In addition, each relay 88. In addition to the type that uses a permanent magnet to maintain operation, the SH may also use a type that maintains operation mechanically, and the control unit CNT may be configured by combining various logic circuits without using a processor. Various modifications are possible, such as using a dedicated one with a similar configuration.

〔Effect of the invention〕

As is clear from the above explanation, 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 handset is reliably rang by the howler sound, and a remarkable effect can be obtained 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 r L'2...Line terminal, H8, H8-fist...Hook switch, TKO...Telephone circuit, SW...
...Switch, DI, D2...Diode, ZD
Ie-- Constant voltage diode, CNTl111... Control unit, 5H-- Release relay, 5S-- Blocking relay, as, ah - ah @... Contact. Patent applicant Tamura Electric Manufacturing Co., Ltd. Nippon Telegraph and Telephone Public Corporation

Claims (1)

[Claims] In public telephones of the pre-loop system that make it impossible to receive calls at least by off-hook, there is a switch inserted into the loop circuit, and a switch that is activated when the normal operation is not performed within a certain period of time after off-hook. A call receiving control circuit for a public telephone set, comprising: a control unit that turns off the telephone; and a release relay that maintains operation in response to turning off the switch, releases the disabled state of receiving calls, and recovers in response to on-hook. .