JPS6230362Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a public telephone circuit, and more particularly to a public telephone circuit that is shared by different types of exchanges such as telephone-controlled exchanges and exchange-controlled exchanges. In some foreign countries, long distance calls may not be made from desk public telephones. However, in these countries, general subscriber lines and public telephone lines are commonly connected to one exchange, so only long-distance calls from public telephones are prevented, and long-distance calls from general subscriber phones are prevented. Identification was necessary to enable transmission. For this reason, the exchange sends a fleeting test reversal signal (instantaneous polarity reversal signal) to the terminal telephone side during hook-off, etc., and any telephone that forms a loop of this instantaneous polarity reversal signal is determined to be a general subscriber telephone. On the other hand, telephones that did not form a loop were judged to be public telephones and prevented from being used for long-distance connections. In such telephones, there was no problem when an AC signal such as 16KHz arrived as a charging signal, but when a polarity reversal signal arrived as a charging signal, the instantaneous polarity reversal signal was used as the charging signal. Some kind of countermeasure had to be taken to prevent coins from being mistakenly stored. For example, in a type of switch that is broadly classified based on the function of the instantaneous polarity reversal signal and is generally called a switch control type switch, when the handset is raised on the terminal side telephone,
An instantaneous polarity reversal signal is sent from the exchange to the terminal side, and the public telephone
By making the inside of the telephone high-resistance, the exchange is configured to be able to identify whether it is a regular telephone or a public telephone, and when a long distance dial is made from a public telephone, the exchange controls the telephone and connects to the long distance. The type is the same as the above type except that an instantaneous polarity reversal signal is sent by the exchange during the first rotation of the dial. In this type and model, the exchange side also performs the identification of public telephones and regular telephones, and the identification of local and out-of-town telephones, for example,
When an instantaneous polarity change signal arrives, the telephone side is set to high resistance, and when the user uses a public telephone to make a long distance dial, the exchange determines that the call is a long distance call and connects. No, so-called exchange control is carried out, and it is configured to prevent long-distance calls before the momentary polarity reversal signal arrives. After completion, the charge signal receiving circuit is connected to the central office line using a relay contact to prevent coins from being erroneously deposited. Therefore, conventional public telephones of this type require a relay or the like to separate the office line from the billing signal receiving circuit, and have the disadvantage that the relay drive circuit is also complicated. In view of the above points, the present application has been made in order to eliminate such drawbacks, and its purpose is to provide a public telephone circuit that does not require any relays, is fully electronic, and has an extremely simple circuit configuration. There is a particular thing. In order to achieve this purpose, the present invention
A thyristor is connected to one side of a diode bridge circuit that forms a polarity reversal loop connected between communication lines, and the thyristor is gated and triggered by the arrival of a polarity reversal signal with a predetermined time width or more, and the thyristor turns.・Depending on the on-current, the above diode
A polarity reversal signal detection circuit connected to one side forming a polarity reversal loop of a bridge circuit is operated.Embodiments of the present invention will be described in detail below with reference to the drawings. The figure is a circuit diagram showing an embodiment of the public telephone circuit according to the present invention. Only the parts necessary for explanation are shown, and the figure shows the case of a first loop type public telephone. In the figure, L ₁ and L ₂ are office line terminals connected to the office line, and a series circuit of a bell BELL and a capacitor C ₁ is connected between the office line terminals L ₁ and L ₂ via a hook switch HS. There is. D ₁ , D ₂ , D ₃ , and D ₄ are diodes, which constitute a diode bridge circuit connected between the communication lines. Pd is a light emitting element, Pt is a light receiving element that receives light from this light emitting element Pd, these form a photocoupler PC, and the light emitting element Pd that forms this photocoupler PC
constitutes a polarity reversal signal detection circuit connected to one side forming a polarity reversal loop of the diode bridge circuit. R ₁ and VR are resistors and varistors connected in parallel in a series circuit with resistor R ₂ connected in series with light emitting element Pd, D ₅ is a diode connected in series with diode D ₄ , R ₃ and R ₄ are connected in series. With the resistance
This series circuit of resistors R ₃ and R ₄ is connected in parallel to a diode D ₅ . _C2 is a capacitor connected in parallel to resistor _R3 , and SCR is a thyristor connected in parallel to the series circuit of resistors _R3 and _R4 , that is, connected to one side of the diode bridge circuit forming a polarity reversal loop. The gate electrode of the thyristor SCR is connected to the connection point of _resistors R ₃ and R ₄ and _the connection point of capacitor C _{2 .}
constitutes a gate trigger circuit that gates and triggers the thyristor SCR by the arrival of a polarity inversion signal with a predetermined time width or more. and thyristor
The turn-on current of the SCR is configured to operate a polarity reversal signal detection circuit consisting of a light emitting element Pd. Further, this capacitor _C2 constitutes a malfunction prevention circuit for instantaneous polarity reversal signals. The light receiving element Pt, which receives the light emitted from the light emitting element Pd, is connected in series with a resistor _R5 , and from that connection point, a billing signal reception signal is transmitted through an inverter _INV1 , resistors _R6 , _R7 , and an inverter _INV2 in series. Configured to send out SG. C ₃ is resistance R ₆ , R ₇
This is a capacitor inserted between the connection point and ground. POW is a power supply circuit for the logic circuit (control circuit) and coin storage magnet (not shown), FR is a forced disconnection circuit that forcibly opens the office line by the output of a control circuit (not shown), and DPG is a mechanical dial impulse. A dial pulse generation circuit consisting of contacts and a short circuit controlled by a control circuit,
TC is a call circuit, and _Ds is a shunt contact of the dial that is activated by turning the dial and is restored just before the end of the release to short-circuit the call circuit TC. Next, the operation of the embodiment shown in this figure will be explained.
First, when you raise the handset, the station line terminal L ₁ (+) - Hook switch HS - Diode D ₁ - Power supply circuit POW - Forced disconnection circuit FR
−Dial pulse generation circuit DPG−Talking circuit
TC - Diode D ₂ - Station line terminal L ₁ (-)
...The loop of (1) is formed and dialing becomes possible. At this time, from the exchange side at any timing (during hook-off, dialing),

[Table] Instantaneous polarity reversal signal (100ms ~
150ms) is sent. Here, the resistances R ₃ and R ₄
Since is of high resistance, capacitor _C2 is charged with only a small current and therefore the thyristor
SCR is not triggered by the time width of the instantaneous polarity reversal signal. In addition, in the loop (2) of the central office line L ₂ (+), resistors R ₃ and R ₄ have high resistance, so on the exchange side, it can be distinguished from a general subscriber telephone, and it is possible to prevent long-distance connections. I can do it. At this time, the photocoupler PC for receiving billing signals
A small current also flows through the light-emitting element Pd that forms the photocoupler PC, but the light-emitting element Pd does not emit light, or even if it does, it does not exceed the threshold hold of the light-receiving element Pt that is paired with the light-emitting element Pd and forms the photocoupler PC. Therefore, the billing signal reception signal SG is not output. After that, a billing signal (550ms) is sent by the called party's response.
or polarity reversal threshold), the thyristor SCR is triggered and turned on after a predetermined time exceeding the time of the instantaneous polarity reversal signal. Then, the light emitting element Pd emits light due to this turn-on current, and the light receiving element Pt receives this and outputs the billing signal reception signal SG. In addition, in conventional public telephones of this type,
Although the capacitor _C3 on the light receiving side prevented malfunctions due to noise, there was a risk of malfunctions due to relatively long noise. However, in the present invention, since the capacitor _C2 constituting the malfunction prevention circuit for the instantaneous polarity reversal signal also functions to prevent malfunctions due to noise, malfunctions can be completely prevented. The present invention has been described above using as an example the case of the first loop which forms a loop before coin insertion, but the same applies to the case of the latter loop which forms a loop after coin insertion. As is clear from the above explanation, according to the present invention, with a simple all-electronic circuit configuration that does not use relays, etc., it is possible to prevent incorrect coin storage due to instantaneous polarity change signals, and to prevent noise. Since malfunctions can be completely prevented, the practical effect is extremely large.

[Brief explanation of the drawing]

The figure is a circuit diagram showing an embodiment of the public telephone circuit according to the present invention. L1 _{, L2} ...Station line terminal, _D1 to _D4 ...Diode, Pd...Light emitting element, Pt...Light receiving element, PC...
Photocoupler, SCR...Thyristor, R ₃ , R ₄ ...
…Resistor, C ₂ …Capacitor.

Claims (1)

[Scope of utility model registration request] In a public telephone circuit comprising a diode bridge circuit connected between telephone lines and a polarity reversal signal detection circuit connected to one side of the diode bridge circuit forming a polarity reversal loop, the diode bridge circuit a thyristor connected to one side forming a polarity reversal loop, and a gate trigger circuit that gates and triggers the thyristor upon arrival of a polarity reversal signal having a predetermined time width or more, the turn-on current of the thyristor A public telephone circuit characterized in that the polarity reversal signal detection circuit is operated by.