CN2196349Y - Telephone anti-theft device - Google Patents

Abstract

The anti-theft device for telephone is composed of single-direction current-detecting circuit and alarm circuit, the current-detecting circuit can be a monostable trigger or a photoelectric isolating circuit with reverse parallel diode. When the telephone is not used or a user normally uses the telephone, the working current can smoothly pass through the burglar alarm, and the current detection circuit and the alarm circuit do not act; when the telephone line or the number is stolen, the reverse current generated in the telephone line is detected, the current detection circuit triggers the alarm circuit to send out an alarm, and the telephone can be found in time and prevented from being stolen by people.

Description

Device for theft-proof of telephone

The utility model relates to a kind of Device for anti-fraudulent use telephone line, a kind of alarm that prevents that telephone line or sign indicating number from number being usurped by the people.

At present phone is universal day by day, along with the personnel that grasp the telephonic communication technology increase, usurps other people telephone line or sign indicating number number, to steal telephonic case also more and more.This class case is illegal wiretapping on the circuit between the switch of subsets and telecommunication bureau mostly, and another telephone set in parallel is to reach the purpose of " gratuitously " conversation.And stolen telephone subscriber is difficult to find whether the phone of oneself is stolen, has both made and has realized telephone charges with overspend undesiredly, also can only look for the telecommunication department negotiation; Telecommunication department can only be overspend serious user's emphasis to minority and check circuit, could find appropriator.When stealing with circuit for those at every turn patch usurp the family, then be difficult to discovery.

In order to address the above problem, the utility model provides a kind of Device for anti-fraudulent use telephone line, and it can in time be found, and send warning when phone be usurped by the people, takes place to prevent the situation of usurping phone.

The principle and the scheme that realize this invention task are as follows: the regular phone machine has faint electric current and passes through when not using on the circuit, this mainly be telephone set keep electric current (being no more than 3mA), in use, electric current can increase to nearly 50mA.These two kinds of senses of current are consistent.When fraudulent use of telephone, the electric current on the circuit is reverse flow immediately, in time detects this reverse current, can find to usurp phenomenon.Concrete scheme is: unidirectional galvanometer circuit of serial connection on telephone line, this galvanometer circuit circuit taking alarm.When usurping, reverse current is detected by galvanometer circuit, and starts warning circuit work, sends warning.Wherein trigger can be the photoelectric isolating circuit of a diode and a reverse parallel connection, for example: TLP521 or TIL113, also can be a monostable flipflop (for example: the 74LS123 trigger); Warning circuit can be a sound chip, drives loud speaker, also can be buzzer or warning bulb.

The utility model can in time detect the reverse current of subscriber phone when being usurped by the people, and report to the police immediately, can in time find to usurp the situation of phone like this, no matter be to overlap the fixing line of usurping, interim overlap joint electric wire when still at every turn usurping, phone was being usurped at that time in the capital, was in time found, can prevent this class phenomenon effectively.

Now be described further with embodiment in conjunction with the accompanying drawings.

Fig. 1 is the electrical schematic diagram of embodiment.

Embodiment: with reference to Fig. 1, diode D of serial connection on the circuit of telephone set ₁, with diode D ₁In parallel, oppositely meet a TLP521 photoelectric isolating circuit U ₁U ₁In photodiode anodal by current-limiting resistance R ₁Meet storage capacitor C ₄Ground connection again, its negative pole is through current-limiting resistance R ₄Connect collector electrode, and meet sound chip MUS and filter capacitor C simultaneously ₃, C ₃Other holds ground connection.U ₁Emitter is through resistance R ₂Ground connection, and simultaneously through resistance R ₄Meet MUS and filter capacitor C ₂, C ₂Other holds ground connection.Other two pin of MUS respectively ground connection with meet loud speaker sp, another termination voltage-stabiliser tube WD of sp ₂With filter capacitor C ₁, and simultaneously through resistance R ₆Meet diode D ₁Positive pole, WD ₂With C ₁Hold ground connection, resistance R in addition ₂In parallel with sp.

When telephone set normally used, electric current was through diode D ₁Flow to telephone set, other circuit is not worked.When usurping, produce reverse current, this electric current is by D ₁Stop, U must flow through ₁Photodiode, make U ₁Triggering and conducting raises the current potential of chip MUS, starts working, and peripheral circuit drives loud speaker and sends warning to chip MUS power supply.Filter capacitor can prevent the working signal and the audio signal interference warning circuit of telephone set.Voltage-stabiliser tube and current-limiting resistance guarantee that warning circuit obtains suitable operating current.

Claims (4)

1, a kind of Device for anti-fraudulent use telephone line is serially connected on the telephone wire of telephone set, it is characterized in that unidirectional galvanometer circuit of serial connection on telephone wire, and this circuit connects a warning circuit.

2, according to the described Device for anti-fraudulent use telephone line of claim 1, it is characterized in that said folk prescription to galvanometer circuit is: a diode and a photoelectric isolating circuit in parallel with diode reverse.

3,, it is characterized in that said folk prescription to galvanometer circuit is: monostable trigger according to the described Device for anti-fraudulent use telephone line of claim 1.

4, according to the described Device for anti-fraudulent use telephone line of claim 2, it is characterized in that: diode D of serial connection on the route of telephone set ₁, with diode D ₁In parallel, oppositely meet a TLP521 photoelectric isolating circuit U ₁, U ₁In photodiode anodal by current-limiting resistance R ₁Meet storage capacitor C ₄Ground connection again, its negative pole is through current-limiting resistance R ₄Connect collector electrode, and meet sound chip MUS and filter capacitor C simultaneously ₃, C ₃Other holds ground connection, U ₁Emitter is through resistance R 2 ground connection, and the while is through resistance R ₄Meet MUS and filter capacitor C ₂, C ₂Other holds ground connection, other two pin of MUS respectively ground connection with meet loud speaker sp, another termination voltage-stabiliser tube WD of sp ₂With filter capacitor C ₁, and simultaneously through resistance R ₆Meet diode D ₁Positive pole, WD ₂With C ₁Hold ground connection, resistance R in addition ₂In parallel with sp.