JPS6214150B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a public telephone set that forms a dialing loop when an emergency call button is pressed, and is equipped with a circuit for preventing unauthorized dialing. Conventional public telephones with emergency call buttons installed in stores, on the streets, etc. have a special dialing mechanism that operates only when you press the emergency call button and then dial 110 or 119 when making an emergency call. As a result, calls can be made only to the specific numbers listed above, making the call free of charge, but even if you press the emergency call button and dial a number other than these numbers, a call loop will not be formed. In addition, in large public telephones for street use, when the emergency call button is pressed, a ground signal is sent to the station, and an additional device installed inside the station secures a free call path only for numbers 110 and 119. When dialing a number other than a specific number, we have added a function that disconnects the call path within the station when the other party answers the dialing call.
Users are no longer able to talk to any other party for free. In this way, in conventional public telephones of this type,
Prevents unauthorized calls when a user presses the emergency call button in a non-emergency situation, configures a dialing circuit, dials an arbitrary subscriber, and attempts to make a free call to that subscriber. In order to
It has the disadvantage of requiring expensive mechanical devices such as a complicated special dialing mechanism or additional equipment within the station. In order to eliminate these drawbacks, the present invention provides a public telephone that can prevent unauthorized calls by operating an emergency call button with an extremely simple circuit configuration without using any special mechanical devices. The present invention will be explained in detail below using the drawings.
FIG. 1 shows an embodiment of a public telephone circuit according to the present invention. Parts not necessary for explanation have been omitted. Figure 2 shows the polarity inversion pulses that are supplied from the station to the calling party's telephone when the other party is called by normal dialing and the called party answers, and Figure 3 shows the polarity inversion pulse that is supplied from the station to the calling party's telephone when an emergency call or incoming toll-free call is made. A signal supplied from a station to a calling telephone, in which case it does not change polarity even if the called party answers. In Fig. 1, L1 and L2 are the central line connection terminals of public telephones, and HS1, HS2, HS3, and HS4 are operated by lifting the handset with a telephone switch.
This is a contact that operates until it is hooked back up. X is a response monitoring relay that operates with a polarity reversal pulse supplied from the station and recovers by hanging up the handset, and _x1 is its contact point. Y is a self-holding relay that is activated by the operation of the emergency call button B and operates until the handset is hung up during a normal call, and is the first circuit switching means in the claims; y ₁ , y ₂ is the contact point, which is the circuit switching section of Y. B is an emergency call button; when the user presses the button, it moves to the D4 side, and when the user releases the button, it moves to the D1 side.
Return to the side. Circuit H is in a state where coins are stored in the storage preparation position or when a toll call condition is established in which a high level is output while the toll call condition is met from the time when money is stored due to reception of a billing pulse until the next billing pulse is received. This is an information output circuit. OA is a current detection unit that detects the current that is intermittent by dial operation, and circuit G counts the output of current detection unit OA and detects when it reaches a certain number of digits (four digits in this case). The dial digit number identification circuit outputs a high level to the dial digit number identification circuit, and the dial digit number detection means referred to in the claims is constituted by a current detection section OA and a dial digit number identification circuit G. Although a well-known current detection element such as a photocoupler or a reed relay can be used for the OA, this embodiment will be explained using a photocoupler. In circuit F, the output of circuit H is high level (the paid call condition is met) or the output of circuit H is low (the paid call condition is not met, that is, the call is made by pressing the emergency call button B). ), which operates when the output of _the circuit G is at a high level, and which recovers by hanging _back the handset; ₃ is its circuit switching section.
N is the call circuit, Di is the dial impulse contact,
Ds is dial-off normal contact, D1, D2,
D3, D4, D5, D6, D7, D8, D9, D
10 is a diode. In addition, Tr is a relay LP driving transistor, R
1, R2 is a current limiting resistor, JKFF1, JKFF
2 is JK flip-flop, RSFF is set-reset flip-flop, NA1, NA2, NA
3, NA4 is a NAND element, I1, I2, I3 are inverter elements, CP is a clock pulse input, S
is a set input, R is a reset input, Q is a positive logic output, and Q is an anti-logic output. In public telephones with such a configuration, when a three-digit emergency call is made by operating the emergency call button B, even if the called party answers, the subscriber line current does not change polarity as shown in Figure 3, so the call cannot be made. This is possible with the loop shown below. First, by operating emergency call button B,
Relay Y, which is the circuit switching means, is [terminal L1 (+) → hook switch HS2 (operation) →
Contact x ₁ → Diode D5 → Contact LP ₂ → Relay Y → Emergency call button B (operating) → Contact Y ₁ (closed) → Diode D4 → Terminal L2 (-) ……(1) Operates in a loop. When relay Y operates and holds itself, [terminal L1 (+) → hook switch HS2 → contact x ₁ →
Diode D5 → contact lp ₂ → contact y ₂ (operation) → dial impulse contact Di → speech circuit N → current detection element OA → diode D8 → terminal L2 (-)] ...(2) A loop with the station is formed. , it becomes possible to make dial calls. The current detection element OA is in this loop, and detects the presence of current before and after the dial and during the pause between digits of the dial (dial impulse contact Di closed and dial-off normal contact Ds open) (the light emitting diode LD emits light and the phototransistor
PT becomes conductive) and outputs a low level to the dial digit number identification circuit G. When the dial is operated, the dial-off normal contact Ds closes, [Terminal L1 (+) → Hook switch HS2 → Contact x ₁ →
Diode D5 → Contact lp ₂ → Contact y ₂ → Dial impulse contact Di → Dial-off normal contact Ds →
Terminal L2 (-)〕 ...(3) loop is formed and the dial impulse contact
A dial impulse is sent out by turning on and off Di, but the dial-off normal contact Ds operates (closes) in the current detection element OA and no current flows, so OA detects that the dial has been operated (light-emitting diode LD (extinguishes and the phototransistor PT becomes non-conductive), and outputs a high level to the dial digit identification circuit G. When the transmission of the first digit (single digit) on the dial is completed, the state returns to (2) again. In this way, dialing up to 3 digits is performed, and when the called party answers, the response signal shown in Figure 3 comes as described above, but the polarity does not change and the call can be made as is in the loop (2). . At this time, the dial digit number identification circuit G does not send a high level to the second circuit switching means F since the number of dial operations is up to three digits, so the contact of the relay LP which is the circuit switching part of the second circuit switching means lp ₁ , lp ₂ , lp ₃ do not work. When the call ends, the first circuit switching means relay Y is restored in the next loop by hanging up the handset. [Terminal L1 (+) → Hook switch HS1 → Diode D1 → Emergency call button B → Relay Y → Contact y ₂
(Operation) → Dial impulse contact Di → Call circuit N → Current detection element OA → Diode D8 → Terminal L2
(-)〕 ...(4) On the other hand, if you attempt to make an unauthorized call using emergency call button B with a dial number of 4 or more digits,
As explained in loops (2) and (3), the current detection element
The OA detects the dial operation, counts this with the dial digit number identification circuit G, and when the number of dial operations reaches 4, outputs a high level to the second circuit switching means F, and the second circuit The circuit switching section of the switching means is operated and the circuit switching section contact _lp2 is disconnected, so that the dial transmission loop (3) is disconnected and no further dial impulses can be transmitted. Therefore, it is possible to prevent a paid call from being made to a called party whose dial number is four or more digits by pressing the emergency call button. Note that when dialing when inserting normal coins, the circuit H is configured to output a high level when the paid call condition is met, so this is received by the second circuit switching means F and relayed. This is done by operating the LP and operating the circuit switching units lp ₁ , lp ₂ , lp ₃ to form the next loop. [Terminal L1 (+) → Hook switch HS2 → Contact x ₁ →
Diode D5 → Contact lp ₂ (operation) → Contact y ₂ (recovery) → Dial impulse contact Di → Call circuit N
→Current detection element OA→Diode D8→Terminal L2
(-)] ...(5) In this case, relay Y, which is the first circuit switching means,
does not work because loop (1) cannot be formed. When the other party (called party) answers, the polarity reversal pulse shown in FIG. 2 is sent, and the response monitoring relay X operates in the next loop. [Terminal L2 (+) → Contact lp ₃ (operation) → Diode
D7 → Call circuit N → Dial impulse contact Di →
Contact y ₂ (recovery) → contact LP ₂ (operation) → diode
D6→Hook switch HS3→Relay X→Diode D2→Terminal L1 (-)] ...(6) After the response monitoring relay X operates, the call is carried out in the next loop. Note that money storage is performed by another well-known control mechanism.

[Table] As explained above, the present invention uses an extremely simple circuit configuration to forcibly disconnect the dialing loop when dialing, without using a complicated special dialing mechanism or a line compatible device in the office, and connects the public telephone and the in-office. Since it is possible to control the communication path to and from the terminal, there is an advantage that the device can be simplified and the cost can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the basic configuration of an embodiment of the present invention, and FIGS. 2 and 3 are signal waveform diagrams for explaining the present invention. Y...Coil part of the emergency call relay which is the first circuit switching means, _y1 , _y2 ...Contacts which are the circuit switching part of the relay Y, F...Second circuit switching means,
lp ₁ , lp ₂ , lp ₃ ...Contacts that are circuit switching parts of the second circuit switching means F, OA...Current detection element that detects the presence or absence of a transmission loop and the presence or absence of a direct current flowing through OA during dial operation , G...The dial digit number identification circuit and the dial digit number detection means are composed of OA and circuit G. H...Signal of accumulation of unaccommodated coins,
Money storage processing confirmation signal and billing pulse 3
Paid call condition establishment information output circuit that outputs information on the establishment of paid call conditions from the input, B... Emergency call button, Di... Dial pulse contact, Ds... Dial-off normal contact, N... Call circuit, X... …
Response monitoring relay, x ₁ ...Relay X contact, HS
1, HS2, HS3, HS4...Hook switch contact, Tr...Relay LP driving transistor, D1
~D10...Diode, R1, R2...Current limiting resistor, JKFF1, JKFF2...JK flip-flop, RSFF...Set-reset flip-flop, NA1, NA2, NA3, NA4...
NAND element, 11, 12, 13...inverter element, CP...clock pulse input, S...set input, R...reset input, Q...positive logic output of flip-flop, Q...anti-logic output of flip-flop. .

Claims (1)

[Scope of Claims] 1. In a public telephone set that forms a dialing loop when an emergency call button is pressed, the system detects and counts the direct current that is intermittent due to dialing operations, and performs dialing operations of a certain number of digits or more. a dial digit number detection means for detecting the number of dial digits, a first circuit switching means activated by pressing the emergency call button, and a first circuit switching means activated by pressing the emergency call button; and a second circuit switching means that is activated by the output from the dial digit number detection means when a dial operation of more than the number of digits is performed, and the circuit switching parts of the two circuit switching means are respectively connected to a dial transmission circuit. Public telephones are connected in series so that a dialing loop is formed when one of them is operated.