CN2201759Y - Anti-theft device for telephone line - Google Patents

Abstract

The utility model relates to an anti-theft device for a telephone line, which is characterized in that an incoming line of the telephone line is connected with the input of a stabilized power supply circuit, and is connected with the control end of a multi-resonant oscillation circuit via a partial pressure sampling circuit at the same time; the power supply end of the multi-resonant oscillation circuit is connected with the output of the stabilized power supply circuit, and the output of the multi-resonant oscillation circuit is connected with the input of an electronic switch circuit; the output of the electronic switch circuit is connected with the incoming line of the telephone line in parallel; current detection circuits are connected in series between the incoming line of the telephone line and a connection line of a user telephone; the output of the current detection circuits is connected with the control end of the multi-resonant oscillation circuit.

Description

Anti-theft device for telephone line

The utility model relates to a kind of servicing unit of telephone line, particularly prevents the device of phreaking.

Along with Chinese economic development, telephone set entered the ordinary people man in a large number in recent years.But existing telephone set does not all have the anti-device of usurping, because outside circuit is exposed to, to a few peoples opportunity is arranged, adopting doubling and insertion pin to usurp other people phenomenon of phone occurs repeatedly, both brought bigger economic loss to telephone user, also bring a lot of troubles to telecommunication administration, have in addition dispute takes place solves to law court.

The purpose of this utility model is exactly in order to address the above problem, and a kind of telephone line alarm that can prevent reliably that other people from usurping is provided.

Technical solution of the present utility model:

A kind of telephone line alarm, it is by voltage-stabilized power supply circuit, pressure sampling circuit, multi-resonant oscillating circuit, electronic switching circuit, current detection circuit is formed, it is characterized in that telephone line inlet wire A, B connects the input of voltage-stabilized power supply circuit, connect pressure sampling circuit simultaneously, the sampling point of pressure sampling circuit is connected with the control end of multi-resonant oscillating circuit, the power end of multi-resonant oscillating circuit is connected with the output of voltage-stabilized power supply circuit, the input of its output termination electronic switching circuit, the output of electronic switching circuit is attempted by telephone line inlet wire A, on the B, at telephone line inlet wire A, B and subsets wiring L ₁, L ₂Between be connected in series current detection circuit, the output of current detection circuit connects the control end of multi-resonant oscillating circuit.

The utility model is connected between telephone line inlet wire and the subsets, in case when having the people on the outdoor circuit of telephone set, to usurp, the utility model moves at once, make two inlet wire short circuits of telephone line, therefore usurp phone and can't work, solved the stolen problem of telephone line effectively owing to no feed voltage.The utility model circuit is simple, and cost is low, anti-usurps effectively, and power consumption is very little, can not produce any influence to whole telecommunications network, for the conversation of subsets itself also without any influence.In addition, the utility model also has functions such as indication of telephone line broken string and anti-eavesdrop.

Fig. 1 is an electrical schematic diagram of the present utility model.

As Fig. 1, voltage-stabilized power supply circuit can be for by transistor BG ₁, voltage-stabiliser tube DW, resistance R ₆, capacitor C ₁The series regulator of forming (also can be the parallel connection type stabilized voltage power supply of being made up of resistance, electric capacity and voltage-stabiliser tube, should seal in diode this moment on its input circuit, to prevent energy storage capacitor discharge when electronic switching circuit is closed), its input is BG ₁Collector electrode be connected with telephone line inlet wire A or B, its output is BG ₁Emitter-base bandgap grading connect the positive power source terminal of multi-resonant oscillating circuit, multi-resonant oscillating circuit can be by not gate G ₂, G ₃, capacitor C ₂, C ₃, resistance R ₃, R ₄Form (also can be the multivibrator that is made of the transistor discrete component or is made of integrated circuits such as NAND gate, NOR gate), its control end is R ₃An end by not gate G ₁Meet pressure sampling circuit R ₁, R ₂Sampling point C, pressure sampling circuit R ₁, R ₂Be attempted by on telephone line inlet wire A, the B, the input of multi-resonant oscillating circuit is G ₃Output connect by multiple tube BG ₂, BG ₃The input (electronic switching circuit also can be made of field effect transistor, turn-off SCR) of the electronic switching circuit of forming, electronic switching circuit output is BG ₂Collector and emitter be attempted by on telephone line inlet wire A, the B, current detection circuit can be two-way, can be respectively by resistance R ₇, transistor BG ₄And resistance R ₈, transistor BG ₅Form (also can constitute), wherein R by photoelectric coupled device ₇, R ₈Be attempted by BG respectively ₄And BG ₅Base stage and emitter-base bandgap grading between, by BG ₄, R ₇Two inputs of the current detection circuit of forming are BG ₄Emitter-base bandgap grading and base stage respectively with telephone line inlet wire A and subsets wiring L ₁Connect, by BG ₅, R ₇Two inputs of the current detection circuit of forming are BG ₅Emitter-base bandgap grading and base stage respectively with telephone line inlet wire B and subsets wiring L ₂Connect, the output of two current detection circuits is BG ₄And BG ₅Collector electrode respectively by backward diode D ₅, D ₆Another control end that connects multi-resonant oscillating circuit is not gate G ₂Input (also can be connected to the input of electronic switching circuit or the output of voltage-stabilized power supply circuit), between telephone line inlet wire A, B and pressure sampling circuit, voltage-stabilized power supply circuit and electronic switching circuit, connect by bridge rectifier D ₁-D ₄The polarity correction circuit that constitutes, so as the utility model not polarity insert on the telephone line.

In the utility model when work, do not have off-hook and telephone line not to have when stolen at subsets, comprises that phone squeezes under the ringing condition, and then the mean direct voltage on the telephone line is through pressure sampling circuit R ₁, R ₂Obtain a level"1" signal at sampling point C, through not gate G ₁After shaping is anti-phase, obtain level "0", make multi-resonant oscillating circuit G at the E point ₂, G ₃Failure of oscillation, and make G ₃So the output level "0" is electronic switching circuit BG ₂, BG ₃By turn-offing, do not influence the operating state of telephone line.When subsets off-hook or telephone line were stolen, C point current potential descended, and becomes level "0", and the E point is a level"1".If subsets off-hook, then two current detection circuit BG ₄, R ₇And BG ₅, R ₈Central must have a positively biased circuit turn-on, and the output level "0" is through D ₅(or D ₆) make D point current potential be " 0 ", so just make multi-resonant oscillating circuit G ₂, G ₃Still be the failure of oscillation state, electronic switching circuit BG ₂, BG ₃Still by turn-offing, thus whole telephone line be not affected, but the subsets normal talking.If telephone line is when stolen, BG in two current detection circuits then ₄, BG ₅All end, output is high-impedance state, at this moment multivibrator G ₂, G ₃Under the effect of E point level"1", starting oscillation makes G ₃Export the level "0" of long level"1" and moment, this duty ratio can be by choosing resistance R ₃, R ₄, capacitor C ₂, C ₃Value decide diode D ₇Be used for being C ₂Instantaneous discharge is provided, guarantees the stable of work.At G ₃When exporting long level"1", electronic switching circuit BG ₂, BG ₃Saturation conduction makes telephone line inlet wire A, B short circuit, can't use because of no feed power supply so usurp telephone set.At G ₃During output moment level "0", it is normal that telephone line recovers, simultaneously the capacitor C of one side in voltage-stabilized power supply circuit ₁Whether the charging energy storage detects telephone line on the other hand once more and is still usurping, if then repeat said process, if usurping machine removes, then makes circuit recover normal under the effect of C point high potential.

In the utility model, if suitably choose resistance R in the current detection circuit ₇, R ₈Resistance, can play the anti-eavesdrop effect, its principle is, inserts owing to usurp phone, the electric current of the subsets of then flowing through after the electric current shunting reduces, and makes R ₇Or R ₈On pressure drop less than 0.7V, BG then ₄Or BG ₅End, make current detection circuit be output as high-impedance state, the multivibrator vibration with telephone line inlet wire A, B short circuit, reaches the function of anti-eavesdrop.As in voltage-stabilized power supply circuit, being connected in series luminous tube on the voltage-stabiliser tube DW, then can be used to play telephone line broken string deixis.

Claims (5)

1, a kind of telephone line alarm, it is by voltage-stabilized power supply circuit, pressure sampling circuit, multi-resonant oscillating circuit, electronic switching circuit, current detection circuit is formed, it is characterized in that telephone line inlet wire A, B connects the input of voltage-stabilized power supply circuit, connect pressure sampling circuit simultaneously, the sampling point of pressure sampling circuit is connected with the control end of multi-resonant oscillating circuit, the power end of multi-resonant oscillating circuit is connected with the output of voltage-stabilized power supply circuit, the input of its output termination electronic switching circuit, the output of electronic switching circuit is attempted by telephone line inlet wire A, on the B, at telephone line inlet wire A, B and subsets wiring L ₁, L ₂Between be connected in series current detection circuit, the output of current detection circuit connects the control end of multi-resonant oscillating circuit.

2,, it is characterized in that voltage-stabilized power supply circuit can be for by transistor BG by the described telephone line alarm of claim 1 ₁, voltage-stabiliser tube DW, resistance R ₆, capacitor C ₁The series regulator of forming, its input is BG ₁Collector electrode be connected with telephone line inlet wire A or B, its output is BG ₁Emitter-base bandgap grading connect the positive power source terminal of multi-resonant oscillating circuit, multi-resonant oscillating circuit can be by not gate G ₂, G ₃, capacitor C ₂, C ₃, resistance R ₃, R ₄Form, its control end is R ₃An end by not gate G ₁Meet pressure sampling circuit R ₁, R ₂Sampling point C, pressure sampling circuit R ₁, R ₂Be attempted by on telephone line inlet wire A, the B, the output of multi-resonant oscillating circuit is G ₃Output connect by multiple tube BG ₂, BG ₃The input of the electronic switching circuit of forming, the output of electronic switching circuit is BG ₂Collector and emitter be attempted by on telephone line inlet wire A, the B, current detection circuit can be two-way, can be respectively by resistance R ₇, transistor BG ₄And resistance R ₈, transistor BG ₅Form, wherein R ₇, R ₈Be attempted by BG respectively ₄And BG ₅Base stage and emitter-base bandgap grading between, by BG ₄, R ₇Two inputs of the current detection circuit of forming are BG ₄Emitter-base bandgap grading and base stage respectively with telephone line inlet wire A and subsets wiring L ₁Connect, by BG ₅, R ₇Two inputs of the current detection circuit of forming are BG ₅Emitter-base bandgap grading and base stage respectively with telephone line inlet wire B and subsets wiring L ₂Connect, the output of two current detection circuits is BG ₄And BG ₅Collector electrode respectively by backward diode D ₅, D ₆Another control end that connects multi-resonant oscillating circuit is not gate G ₂Input.

3, by claim 1 or 2 described telephone line alarms, it is characterized in that voltage-stabilized power supply circuit also can be the parallel connection type stabilized voltage power supply of being made up of resistance, electric capacity and voltage-stabiliser tube; Multi-resonant oscillating circuit also can be the multivibrator that is made of the transistor discrete component or is made of integrated circuits such as NAND gate, NOR gate; Electronic switching circuit also can be made of field effect transistor, turn-off SCR; Current detection circuit also can be made of Light Coupled Device.

4, by claim 1 or 2 described telephone line alarms, it is characterized in that the output of current detection circuit also can be connected to the input of electronic switching circuit or the output of voltage-stabilized power supply circuit.

5,, it is characterized in that between telephone line inlet wire A, B and pressure sampling circuit, voltage-stabilized power supply circuit and electronic switching circuit, inserting by bridge rectifier D by the described telephone line alarm of claim 1 ₁-D ₄The polarity correction circuit that constitutes.