CN2220139Y - Theft-proof terminal box for telephone - Google Patents

Abstract

The utility model provides a theft-proof terminal box for a telephone, relating to a monitoring anti-theft device for a telephone external line. The utility model is composed of an identification circuit 1, a polarity inversion circuit 2, a detection control circuit 3, a square wave occurring circuit 4 and a filtering closing switch circuit 5, wherein, the output of an RC filtering closing switch circuit of the filtering closing switch circuit is connected with the input end of the detection control circuit; the identification circuit is provided with a photoelectric coupling switch IC1 which can identify abnormal condition signals of the external line and off-hook signals of the user telephone and is connected in series between the telephone and the external line. The utility model can prevent the external line from being embezzled illegally on the foundation of ensuring the user telephone not to be influenced.

Description

The antitheft terminal box of phone

The utility model is relevant with telephone communication, and is especially relevant with the antitheft terminal box of telephonic communication system.

Along with the fast development of urban telephone, steal telephonic incident and constantly occur, the person is attempted by telephoning illegally on the subscribers feeder to the circuit of oneself dexterously to usurp the phone, has made a call immediately and has taken out stitches, thereby be difficult to find.At present, the also not simple effectively prison of huge numbers of families telephone subscriber's outdoor circuit shows protector.

The purpose of this utility model provides a kind of the assurance on this impregnable basis of family phone, the telephone connection box a kind of simple in structure, with low cost that prevents that outside line from illegally being usurped.

The utility model is by identification circuit 1, and polarity transformation circuits 2 detects control circuit 3, square wave generation circuit 4, and filtering lockout switch circuit 5 is accused well circuit 6 and is formed.Polarity transformation circuits 2 is connected to outside line L ₁, L ₂Between, be a bridge rectifier, no matter L ₁, L ₂He Duanwei just can both guarantee to export the A point and be positive polarity.Detect control circuit 3 by sample circuit, dual-time constant delay circuit, the NAND gate control circuit, control Driver Circuit is formed.The input of sample circuit is connected to the A end, and output meets D ₅, R ₄, C ₂The dual-time constant delay circuit that constitutes.The output of delay circuit meets NAND gate control circuit U ₂An input, U ₂The output of another input termination square wave generation circuit 4.Has only U ₂Two inputs when being high level simultaneously, U ₂The ability output low level.U ₂Output meet control Driver Circuit U ₃, U ₃Output connect filtering lockout switch circuit 5.The RC filtering lockout circuit output of switching circuit 5 connects the A point.Identification circuit 1 is by optical coupled switch IC ₁And the peripheral cell composition, all be connected in the telephone set outside line IC with polarity transformation circuits 2 ₁Output connect the input of square wave generation circuit 4.Another exports ground connection, can discern outside line abnormal condition and this family receiver off-book signal.

Polarity transformation circuits of the present utility model 2 is by D ₁-D ₄Four rectifier diodes are formed bridge rectifier.Two inputs of bridge rectifier are connected to L respectively ₁, L ₂On, one output ground connection, another output is connected to the A point.

The sample circuit that detects control circuit is by R ₁, R ₂, U ₁Form.R ₁, R ₂Be serially connected with between A point and the ground R ₁, R ₂Contact meet not gate U ₁Input.Diode D ₅, R ₄Be connected in U ₁Output and NAND gate U ₂Input 1 between, capacitor C ₂Be connected to U ₂Input 1 and ground between, U ₂Output meet not gate U ₃U ₃Output meet switching transistor BG ₁Base stage, be in series with R therebetween ₉R ₁Resistance 〉=10M Ω, take from the electric current＜5 μ A on the outside line, can not influence the operate as normal at telephone exchange networking.Work as L ₁, L ₂During last no phone off-hook, voltage 〉=48V, R ₂Last dividing potential drop gets high level, U ₁Output low level.Otherwise, work as L ₁, L ₂On voltage≤7V, R are arranged and during the telephone set off-hook that connects ₂Go up low level signal, U ₁The output high level is delivered to U through the dual-time delay circuit ₂Input 1.D ₅, R ₄, C ₂Charge constant be about 0.5S, discharge time constant is 100ms, can guarantee at switch during to the ring of this family, in the off time of the tinkle of bells, U ₂Input 1 is still kept low level.And as outside line L ₁, L ₂During to high level, less discharge time constant can make U to last voltage by low level ₂Input 1 reduce to low level rapidly.NAND gate control circuit U ₂The square wave control sent here by square wave generation circuit 4 of another input 2.

Square wave generation circuit 4 is by NAND gate U ₅, U ₆And R ₆, R ₇, C ₃, D ₈Form.Its square-wave cycle is 1-2 seconds, C ₃Be positive feedback electric capacity, be connected to U ₆Input and U ₅Output between.R ₆, R ₇Be connected to U after the series connection ₆Input and output between, D ₈With R ₆Parallel connection can change duty ratio easily.U ₅Output meet U ₂Input 2, have only U ₂Input 1,2 when being high level simultaneously, U ₂Output just is low level.Other situation is all high level.Has only U ₂Output low level, U ₃Just export high-level control signal, drive triode BG on the one hand ₁, make its saturation conduction; Deliver to not gate U on the other hand ₄Input removes to control red light emitting diodes D ₆, make it that alarm signal take place.

Warning circuit is by not gate U ₄, light-emitting diode D ₆, current-limiting resistance R ₅Be composed in series.R ₅Be connected to positive source, power cathode ground connection.Work as U ₄When input is high level, U ₄Output is a low level, D ₆There is forward current to pass through, luminous.Otherwise, not luminous.

Filtering lockout switch electric routing switch triode BG ₁, R ₃, C ₁Form.R ₃, C ₁The filtering lockout circuit of forming one is terminated at BG ₁Collector electrode, the other end is connected to the A point.BG ₁Grounded emitter.When U3 output high level, pass through R ₉Make BG ₁Saturation conduction.R ₃Resistance very little, the A point is reduced to below the 3V, make to be attempted by L ₁, L ₂Phone in the outside line can not be transferred to.C ₁Capacity is bigger, and the dual-tone dialing signal is filtered, and pulse dialing signal becomes smoothly, and switch can't receive at all.

Identification circuit is by optical coupling switch I C ₁And D ₇, R ₈Form.D ₇, R ₈Be connected to IC ₁1,2 pin between, and be serially connected with L ₁On.IC ₁3 pin meet U ₆Input, 4 pin ground connection.R ₈Be shunt resistance, prevent to pass through IC ₁Inner led current is excessive.D ₇With IC ₁1,2 pin provide alternating current path for the bell signal that switch is sent here together.When this family phone off-hook, and L ₁For just, L ₂When negative, just there is electric current to pass through IC ₁Inside, lumination of light emitting diode, IC ₁3,4 pin between conducting, no current during on-hook, IC ₁3,4 pin between resistance very big.

The utility model is simple in structure, and is with low cost, and reliable in function can be serially connected with between subscriber phone and the terminal box easily, circuit is shielded, and the normal talking of this family phone is not affected.

Fig. 1 is a block diagram of the present utility model.

Fig. 2 is the circuit theory diagrams of utility model.

Embodiment of the present utility model is as follows:

(1) monitoring state:

When not having the receiver off-book of parallel operation on the outside line, outside line voltage passes through R ₁With R ₂The sample circuit of forming makes U ₁Be input as high level, U ₁Be output as low level.This low level is delivered to NAND gate U ₂Input 1, U then ₂The output high level is to U ₃, U ₃Output low level makes diode BG ₁Be in cut-off state, filtering lockout switch circuit is not worked.U ₄The output high level, red light emitting diodes is not luminous, and complete machine is in unblocked monitoring state.

(2) blocked styate:

When the phone off-hook of phreaking is arranged in the outside line, R ₂Last sampling obtains low level signal, U ₁The output high level also is sent to NAND gate U ₂Input 1.When square-wave generator is sent into U ₂When input 2 also is high level, U ₂With regard to output low level, U ₃The output high level, BG ₁Be in the saturation conduction state.By R ₃With C ₁The filtering lock circuit of forming makes line voltage distribution reduce to below the 3V on the one hand, makes the phone of usurping circuit can not get normal voltage and can not work.Can carry out filtering to audio frequency or the pulse signal that the telephone set of usurping circuit is transferred to again on the other hand, make switch can't receive its dialing signal, this can not dial phone with regard to the dual telephone set of usurping circuit that guaranteed at all.At U ₃During the output high level, U ₄Output low level, the red light emitting diodes marrow of alarm display circuit the frequency of square-wave generator and is glimmered.At the off time of square wave, BG ₁Also be in cut-off state.

If usurp the telephone set on-hook of circuit, the A level point raises, R ₂On obtain high level signal, U ₂The output high level, circuit is returned to monitoring state again.

(3) this machine talking state:

When the telephone set off-hook of this family, by the photoelectric coupling switch IC of identification circuit ₁The electric current of 1,2 pin make 3,4 pin conductings, make U ₂Input 2 keeps low level.R no matter ₂Last voltage how, U ₂Output all is high level.BG ₁Be in cut-off state, the alarm display circuit is not worked, thereby guarantees the conversation of this family, dialing, receives the operate as normal of bell, has both made not add battery and can guarantee this family phone normal talking, dialing yet.

U in the present embodiment ₁, U ₂, U ₃, U ₄, U ₅, U ₆Be CD4011.BG ₁Adopt A42, IC ₁Adopt photoelectric tube P521-1, D ₁, D ₂, D ₃, D ₄, D ₇Adopt 1N4001 or 1N4007.D ₅, D ₈Adopt the 1N4148 diode.

Claims (3)

1, the antitheft terminal box of phone, it is characterized in that by identification circuit (1), polarity transformation circuits (2), detect control circuit (3), square wave generation circuit (4), filtering lockout switch circuit (5) are accused well circuit (6) and are formed, the output terminals A point of polarity transformation circuits (2) is a positive potential, connect the sample circuit that detects control circuit (3), the output of sample circuit connects dual-time constant delay circuit, and the output of delay circuit meets NAND gate control circuit U ₂An input, U ₂The output of another termination square wave generation circuit (4), have only U ₂Two inputs when being high level simultaneously, U ₂The ability output low level, U ₂Output meet control Driver Circuit U ₃, U ₃Output connect filtering lockout switch circuit (5), the RC filtering lockout circuit of switching circuit (5) output connects the A point, identification circuit (1) is by photoelectric coupling switch IC ₁And the peripheral cell composition, and polarity transformation circuits (2) all is connected between telephone set and the outside line IC ₁An output pin connect the input of square wave generation circuit, another output pin ground connection can be discerned outside line abnormal condition and this family receiver off-book signal.

2, the antitheft terminal box of phone according to claim 1 is characterized in that said polarity transformation circuits is by D ₁-D ₄Four rectifier diodes are formed bridge rectifier, are connected to outside line L ₁, L ₂Between, two inputs of bridge rectifier meet L ₁, L ₂, one output is connected to the A point, and no matter another output head grounding is L ₁, L ₂He Duanwei just can both guarantee that the A point is positive polarity, detects control circuit by sample circuit R ₁, R ₂, not gate U ₁, dual-time constant delay circuit D ₅, R ₄, C ₂, NAND gate control circuit U ₂, control Driver Circuit U ₃Form R ₁, R ₂Be connected between A point and the ground R ₁, R ₂Contact meet U ₁Input, D ₅, R ₄Be connected in U ₁Output and U ₂Between the input 1, C ₂Be connected to U ₂Between input 1 and the ground, U ₂Output meets U ₃Input, U ₃Output meets BG ₁Base stage is in series with R therebetween ₉, R ₁Resistance 〉=10M Ω, square wave generation circuit is by not gate U ₅, U ₆And R ₆, R ₇, C ₃, D ₈Form C ₃Be positive feedback electric capacity, its square-wave cycle is 1～2 second, is connected to U ₆Input and U ₅Output between, R ₆, R ₇Series connection is connected to U ₆Input and output between, can change duty ratio, U easily ₅Output meet U ₂Input 2, U ₆Input be connected to IC ₁3 pin, filtering lockout switch electric routing switch triode BG ₁And by R ₃, C ₁The filtering lockout circuit of forming is formed,

The R of filtering lockout circuit ₃, C ₁Be connected in BG ₁Collector electrode, output is connected to A point, BG ₁Grounded emitter, identification circuit is by optical coupling switch I C ₁And D ₇, R ₈Form R ₈And D ₇Be connected to IC ₁1,2 pin between and be coupled to outside line L ₁On, IC ₁3 pin meet U ₆Input, 4 pin ground connection, R ₈Be shunt resistance, prevent to pass through IC ₁Inner led current is excessive, D ₇With IC ₁1,2 pin provide alternating current path for the bell signal that switch is sent here together.

3, according to claim I or the antitheft terminal box of 2 described phones, it is characterized in that control Driver Circuit not gate U ₃Output connect by not gate U ₄, light-emitting diode D ₆, current-limiting resistance R ₅The warning circuit that is composed in series (6), R ₅Be connected to positive source, power cathode ground connection.

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