CN1073773C - Device for preventing fraudulent use of telephone subscriber line - Google Patents

Abstract

An apparatus for preventing fraudulent use of a telephone subscriber line. It uses a theft detection circuit to detect the output potential of the telephone rectifier to know that the telephone subscriber line is stolen, so as to send out signal to touch the telephone dialer, and send out alarm signal to the telephone subscriber line to interfere the dialing or talking of the telephone of the thief, at the same time, the alarm signal is fed back to the amplifier circuit of the telephone, and the alarm signal is sent out by the amplifier to form alarm sound to inform the user. The invention uses the embezzlement detection circuit to match the existing resources of the telephone, and can achieve the purposes of interfering embezzlement users and informing users under the condition of lowest cost.

Description

Device for preventing telephone subscriber line from being stolen

The present invention relates to a device for preventing telephone subscriber lines from being stolen, in particular to a device for preventing telephone lines from being stolen by using a telephone dialer to emit an alarm signal to interfere with the thief and notify the user.

Phone theft is an annoying problem that often causes considerable damage and is not easy to prevent. And the telephone subscriber line being stolen is exactly wherein common a kind of, because the user is difficult to detect whether there is the pirate of outdoors to use its telephone line, so can't take precautions against.

One of the ways to solve the above-mentioned difficulties is to install a detection device. Figure 1 shows a known technology, which is to install a detection device on the telephone line. Once the thief uses the phone, an alarm sound will be triggered to notify the user that his telephone subscriber line Misappropriation.

The phone 100 includes the components of a general phone and a detection and alarm device. The general telephone line is connected to other lines from the outside line terminal 101 through a rectifier 102, including hook switch 103, receiver detection circuit 104, dialer 105, keyboard 106, loop control telephone 107, communication network and loop load 108, and expansion Audio telephone amplifier circuit 109, these all are the basic devices that constitute the telephone set, and the already clear knowledge of those who are familiar with this technology will not be described in detail here.

The detection and alarm device part is to install a fraud detection circuit 110 connected to the output end of the rectifier 102 . When all the telephones are on-hook, that is, the telephone loops are all in a high-impedance state, the output terminal of the rectifier 102 is at a high potential, such as 48 volts. If the thief steals the telephone line, the loop of the outdoor parallel unit 112 is connected, and the output potential of the rectifier 102 drops to a low potential, such as 12 volts. This potential change is detected by the fraud detection circuit 110, and sends a fraud detection signal UVD to start a sound signal device 111, such as an oscillator or a sound integrated circuit (IC), and its signal output is sent to the buzzer 113 to send an alarm sound. The user then learns that the telephone line has been stolen.

Although the above-mentioned method solves some problems, it is not perfect. For example, the device only provides an alarm function, that is, it only notifies the user itself, and does not wish to have any blocking effect on the embezzler; The ringer 113 needs to increase a lot of cost, which is relatively unfavorable in industrial utilization (commercialization); what is more serious is that no matter the indoor parallel machine or the outdoor parallel machine will touch the device, once the device is installed, it will cause failure to connect. Other indoor extensions. Therefore, it is necessary to improve the technology for preventing telephone subscriber lines from being stolen, so as to avoid above-mentioned various defects.

Therefore, what the present invention intends to achieve is to propose a low-cost device for preventing telephone subscriber line from being stolen, so as to eliminate the disadvantages of the above-mentioned prior art, and achieve the purpose of disturbing the pirate and warning the user at the lowest cost.

In detail, the main purpose of the present invention is to propose a device for interfering with stolen telephones, which can interfere with the dialing or conversation of the stolen phone by sending an alarm signal to the telephone subscriber line.

Another object of the present invention is to provide a device with alarm function, which uses the loudspeaker of the telephone to send out an alarm signal to inform the telephone user that his subscriber line has been stolen.

Another object of the present invention is to disclose a low-cost device for preventing phone subscriber line from being stolen, which makes full use of the existing resources of the phone to interfere with the thief and notify the user, so that the cost of the overall device is reduced to a minimum.

Yet another object of the present invention is to propose a device that allows extensions to be connected in parallel to prevent telephone subscriber lines from being stolen, that is, the device allows telephone users to use extensions in parallel, so that the phone still maintains normal functions.

In order to achieve the above-mentioned purpose, the technical solution of the present invention includes a fraud detection circuit connected to the rectifier and the dialer of the phone respectively, and the fraud detection circuit is an RC charging and discharging circuit composed of Zener diode ZD1 connected in series with resistor R1, resistor R2 and capacitor C1 Circuit configuration, the output from the voltage divider of resistors R1 and R2 is connected to the dialer through the current limiting resistor R3 and diode D1, the contact of resistor R3 and diode D1 is connected to a grounding capacitor C2, and the dialer sends an alarm signal to the telephone subscriber line; Use a misuse detection circuit to connect the rectifier and dialer of the phone respectively. The misuse detection circuit uses the output potential of the rectifier to know that the telephone subscriber line has been misused, thereby touching the dialer and sending a periodic alarm signal to the telephone. Telephone users are on the line to interfere with dialing or talking on the phone of the thief.

Moreover, the alarm signal is fed back to the amplifier loop of the telephone set, and sent out by the amplifier to form a warning tone, informing the user that his subscriber line has been stolen.

In addition, an extension circuit state detection circuit is serially connected between the subscriber line and the extension terminal connected to the subscriber line in parallel, and it detects that the extension connected to the extension terminal is used and sends a signal to make a misuse alarm Function is not touched.

The technical scheme of the present invention cooperates with the existing resources of the telephone set with the embezzlement detection circuit, and can achieve the purpose of interfering with the embezzler and notifying the user under the condition of the lowest cost.

The descriptions of the attached drawings are as follows:

Fig. 1 is a prior art, wherein discloses a kind of embezzlement detection mode;

Fig. 2 shows the situation of indoor parallel machine and outdoor parallel machine (stealer) of the present invention;

Fig. 3 is an embodiment of the present invention;

Fig. 4 is the operation flowchart of the present invention;

Fig. 5 is an operation timing diagram of the present invention.

In Fig. 4, the letter "Y" means "yes", and the letter "N" means "no". By using the following embodiments and cooperating with the attached drawings, the features and effects of the present invention can be understood better.

The telephone paralleling situation of the present invention is shown in Figure 2, and the main telephone 201 in the indoor 200 is provided with outside line connection terminal hole and extension connection terminal, provide and connect the outdoor telephone subscriber line and other indoor parallel machines (extensions) respectively 202, and it is a thief to install the outdoor parallel machine 203 by telephone subscriber line outdoors.

Fig. 3 shows an embodiment of the present invention, the phone 300 utilizes the external line terminal 301 to connect other lines via a rectifier 302, including a hook switch 303, a handset detection circuit 304, a dialer 305, a keyboard 306, a loop control phone 307, and a communication network And the loop load 308, and the loudspeaker telephone amplifier loop 309 etc., are still the same as the existing telephone, so it is not much to illustrate.

The feature of the present invention is that the output terminal of the rectifier 302 is connected with a tamper detection circuit 310 to detect the output potential of the rectifier 302 , and the tamper detection circuit 310 provides a tamper detection signal UAD to the dialer 305 .

In this embodiment, the dial mute pin XMUTE is used as the connection between the fraud detection signal UAD and the dialer 305 . The dial mute pin XMUTE is generally used as a mute output control pin when dialing, and in this embodiment is designed as a two-way input and output control pin, which is automatically set as an input pin for fraud detection under standby (when the phone is not in use) Signal input, when the phone is in use (dialing or talking) is automatically set as the output control pin for mute control.

Selecting the dial mute pin XMUTE as the input of the embezzlement detection signal UAD is not a limitation of the present invention, and the connection end of the embezzlement detection signal UAD and the dialer 305 can also be selected in other different designs, such as using a keyboard end, retaining an input/output end or other Available ports serve the same purpose.

When all the telephones are in standby mode, the output terminal of the rectifier 302 is a high potential (about 48 volts), and the embezzlement detection signal UAD is logic 1 at this moment; At this time, due to the formation of the loop of the outdoor parallel machine 312, the output of the rectifier 302 drops to a low potential (about 12 volts), causing UAD to switch from logic 1 to logic 0, and then triggering the loop start control pin of the dialer 305 (such as PO, HDO, HFO, etc.), that is, the loop control circuit 307 and the amplifier loop 309 of the amplified telephone are activated, and the communication network and the loop load 308 are enabled.

After the loop is formed, set the XMUTE pin as an output function and output a low potential signal (mute), and at the same time, the DTMF pin sends an alarm signal, which is transmitted to the telephone subscriber line through the communication network and the loop load 308, which becomes an interference signal Interfere with the dialing or calling of the outdoor parallel machine 312. This alarm signal is fed back to the amplifier circuit 309 of the loudspeaker telephone at the same time, and is sent out by the loudspeaker to form a warning sound to inform the user that his subscriber line has been stolen.

The alarm signal provided by the dialer 305 has many different options, such as a single frequency signal, a music signal, or any signal that the dialer 305 generates by itself enough to interfere with dialing and conversation, and a double-tone signal or pulse signal for telephone dialing can also be used, but, In order to prevent the double-tone signal or pulse signal during the interference period from being mistaken for a normal dialing sequence by the public switching network, the start code of the interference signal excludes the double-tone or pulse signal of the number (0-9) dialing key as much as possible.

The alarm signal sent by the above-mentioned DTMF pin is a signal with a cycle T, and this cycle is called the alarm interference cycle. When the alarm interference period is over, the dialer 305 will automatically return the loop start control pin, such as PO, HDO, HFO, etc., to the initial state, close the phone loop, and automatically set the mute control pin XMUTE as the input of the tamper detection signal Detect pin in order to re-detect the signal from the UAD. If the UAD signal is still logic 0 at this time, indicating that the stolen phone 312 is still in use, the dialer 305 will start the alarm interference cycle again. If the UAD signal becomes logic 1 at the end of the alarm interference period, indicating that the fraudulent phone 312 has been hung up, then the dialer 305 returns to the initial detection state.

During the alarm disturbance period, if the microphone of the telephone set 300 is picked up, the dialer 305 will automatically end the alarm disturbance period, and through the closing of the hook switch 303, the microphone detection circuit 304 sends a signal to the dialer 305 to activate the telephone loop, so that Generally dial and receive calls, or monitor the state of the stolen phone 312.

During the above-mentioned alarm interference period, although the dialer 305 opens the loop of the phone, but this loop is not opened through a program of normal use of the phone, such as picking up the microphone, etc., so the dialer 305 will automatically close the keyboard 306 to make the key invalid. Do not interrupt the alarm interference signal.

The relationship between main signals such as the fraud detection signal UAD and the alarm interference period will be described in more detail later.

Existing inspection of the internal circuit of the embezzlement detection circuit 310, this embodiment uses an RC charging and discharging circuit as the detection circuit. When the output of the rectifier 302 is at a high potential, the Zener diode ZD1 is turned on, and a logic 1 level is obtained at the UAD pin through appropriate voltage division by the resistors R1 and R2. The diode D1 can isolate the interaction between other components in the fraud detection circuit 310 and the communication network and the loop load 308 .

The function of the extension circuit state detection circuit 311 and its internal circuit will be described below. In order to achieve the extra function of parallel connection to the indoor extension, the extension connection terminal 313 is parallel connected to the subscriber line, and the extension loop state detection circuit 311 is connected in series between the two. When the extension connected to the extension terminal 313 is in use, the loop current flows through the resistor R4 to generate a voltage drop, and the optocoupler PHO1 is turned on through the rectifier BR1 and the resistor R5. Although the output potential of the rectifier 302 drops to 12 volts at this time, the conduction of the optocoupler PHO1 keeps UAD at a logic 1 level, so that the UAD signal will not be accidentally triggered by the dialer 305 because the subscriber line is used by an extension. Alarm signal, that is, the present invention allows users to use parallel extensions. Also, the use of PHO1 also has the effect of an isolation circuit. When PHO1 is turned on, R3 has a current limiting function. Prevent large current from VDD to XMUTE pin through PHO1, D1 when XMUTE pin outputs low potential level.

The internal circuits of the above-mentioned embezzlement detection circuit 310 and extension circuit state detection circuit 311 are only embodiments, and are not limitations of the present invention. For those familiar with circuit technology, it is obvious to make various designs for the same function. , still without departing from the spirit of the present invention.

FIG. 4 shows the detailed operation process of the phone 300, please refer to FIG. 3 together.

Under normal conditions, the phone is in a standby state, that is, step 400 is waiting for an external command to activate the phone, such as picking up the handset (Off-Hook) or pressing the handset function (Handfree).

Once the signal for enabling the phone is detected, it will jump to step 406, the dialer 305 will start the call circuit, and set the input terminal XMUTE of the fraud detection signal UAD to the state of the output control function, so as to dial or answer the call.

Then enter step 407, if the dialer 305 detects the signal of the end of the call, such as hanging up the phone or ending the hands-free function, then the input terminal XMUTE of the misappropriation detection signal UAD is set to the detection state of misappropriation detection signal input, and at the same time Execute step 408 to close the call loop, and return to the state of step 400 to continue waiting for the command to activate the phone. The above is the general normal use process of the phone 300 .

In addition, the phone is waiting for the step 400 of enabling the phone, and at the same time it is waiting for the command of fraud detection, that is, step 401 .

Once the phone loop of the thieves is formed and detects that the subscriber line has been stolen, it will enter step 402, and the dialer 305 will automatically start the circuit of the machine to supply the power requirements of the dialer 305 and other devices in the phone, and at the same time send the detection signal The input terminal XMUTE of UAD is set to the output function control state of normal dialing, and the alarm signal is sent out by the dual tone signal terminal DTMF as the interference signal.

The alarm interference signal operates according to the preset cycle period of the dialer 305. When the alarm interference cycle is over, step 403 enters step 408, and the dialer 305 sets the XMUTE terminal to the detection state of the detection input, and closes the call at the same time loop, and get back to step 400 to wait for the state of enabling the phone command.

In this way, if the thief continues to use the subscriber line, the operation process of the phone will automatically execute step 400→step 401→step 402→step 403→step 408→step 400→and so on.

During the default cycle alarm interference period of the dialer 305, if the dialer 305 detects that the phone 300 itself activates the telephone command, that is, enters step 404 from step 403, then executes closing the alarm interference signal and cycle, that is, step 405, and then enters normal The operation flow of the phone 300 is step 406→step 407→step 408, etc. If the thief is still using it, the phone 300 can start monitoring at any time.

If the phone 312 of the hijacker has been turned off during the warning interference cycle, then after the dialer 305 finishes the warning interference cycle, it will automatically return to the initial detection state of step 408→step 400, and the detection signal of misappropriation does not exist now. , so the dialer 305 ends the action of this loop detection alarm interference, until the pirate loop is formed again.

The timing sequence of fraud detection and alarm interference is shown in Figure 5, please also refer to Figure 3 together.

When the outdoor parallel machine 312 is in use, the tamper detection signal UAD of the tamper detection circuit 310 is switched from logic 1 to logic 0. After this signal triggers the dialer 305 to execute for a Tdb time, the PO (HFO, HDO) pin rises from low potential to high potential, making the loop of the phone 300 conduction, and at the same time, the DTMF pin of the dialer 305 sends an alarm signal with a period of T to the phone The loop is used as a signal to interfere with the thief, and this signal is fed back to the amplifying loop 309 of the telephone set 300 or the receiver of the handset as an alarm. T=1.5 seconds in this embodiment.

The above-mentioned period T is automatically set by the dialer 305. When the interference period ends, the PO (HFO, HDO) pin of the dialer 305 drops from a high potential to a low potential, and the telephone 300 circuit is automatically closed, and after a time of Tdb Check the signal of UAD pin again. When Tdb ends, if the UAD signal is still logic 0, the action of the disturbance period T is repeated. The Tdb time is a time to prevent malfunction caused by input signal jitter.

Moreover, the dual-tone (DTMF) alarm interference period T shown in FIG. 5 is composed of a sequence of symmetrical periods of Toff and Ton. In this embodiment, Toff=Ton=250 milliseconds (ms), and the type of its signal is to use the "#" (or "*") number key of the dial key as the starting code, followed by the second "8" number Key, that is, three signals of "#, 8, 8" are a cycle T.

If the outdoor parallel machine 312 is on-hook during the alarm interference period T, the UAD signal will not be converted from logic 0 to logic 1 immediately because the loop of the phone 300 itself is turned on, so after the alarm interference period T is over, the dialer 305 The PO (HFO, HDO) pins drop from high potential to low potential, automatically close the phone 300 circuit, and when the Tdb debounce sequence ends, it can detect that the UAD signal has changed from logic 0 to logic 1, indicating that the stolen phone 312 has hung up. At this time, the alarm interference period ends.

As mentioned above, during the alarm interference period T, if the thief has hung up, the UAD signal cannot return to logic 1 due to the formation of the loop of the phone itself, but when the alarm interference period T ends, the dialer 305 will automatically activate the loop The control pin returns to the initial state, closes the telephone circuit, and makes the UAD signal return to logic 1. Therefore, the alarm interference period must be designed to an appropriate length. If the period is too long, it will not be possible to immediately detect the action of the thief hanging up. According to common people's habits, the alarm interference period is preferably about 1 to 5 seconds.

In the timing sequence of Figure 5, the oscillator OSCO of the dialer 305 oscillates according to the internal timing requirements of the dialer 305 during the period T and the debounce time Tdb, and stops oscillating when the loop of the phone 300 is closed and UAD is detected as logic 1 .

In the sequence of Fig. 5, if the phone 300 itself detects a command to activate the phone, such as lifting the microphone or starting the hands-free handset, the above sequence will be reset, and the phone 300 will be in a state of normal use, and the sequence of this state It is a prior art and will not be described in detail here.

The above description is to utilize the embodiment to illustrate the characteristics of the present invention, and its purpose is only to enable those skilled in the art to understand the content of the present invention and implement it accordingly, rather than to limit the patent scope of the present invention. The equivalent modification or modification completed in the spirit of the reminder shall still be included in the scope of the patent application described below.

Claims (6)

1, a kind of device that prevents fraudulent use of telephone subscriber line, it is characterized in that comprising and usurp rectifier and the dialer that testing circuit connects phone respectively, usurping RC that testing circuit is made up of Zener diode ZD1 series resistor R1 and resistance R 2 and capacitor C 1 charges and discharge circuit and constitutes, be connected to dialer from resistance R 1 and the output of R2 branch pressure side through current-limiting resistance R3 and diode D1, the contact of resistance R 3 and diode D1 is connected a ground capacity C2, and dialer sends an alarm signal to telephone loop.

2, the device that prevents fraudulent use of telephone subscriber line as claimed in claim 1 is characterized in that this usurps testing circuit is to utilize the quiet control end of this dialer to connect with being connected of this dialer.

3, the device that prevents fraudulent use of telephone subscriber line as claimed in claim 1 is characterized in that this usurps testing circuit is to utilize the keyboard end of this dialer to connect with being connected of this dialer.

4, the device that prevents fraudulent use of telephone subscriber line as claimed in claim 1 is characterized in that this usurps testing circuit and being connected of this dialer is to utilize the reservation of this dialer to export into end to connect.

5, the device that prevents fraudulent use of telephone subscriber line as claimed in claim 1, it is characterized in that more comprising that an extension set binding post is connected on this subscriber's telephone line, and be connected in series an extension set loop state testing circuit between this telephone loop and this extension set binding post, this extension set loop state testing circuit also connects this and usurps testing circuit, when wherein this extension set loop state testing circuit detects extension set that this extension set binding post connected and is used, just send a shutdown signal and usurp testing circuit to this and make it can't touch this phone dialer.

6, the device that prevents fraudulent use of telephone subscriber line as claimed in claim 5 is characterized in that this extension set loop state testing circuit is to utilize an optical coupler to export the extension set detection signal conversion generation shutdown signal of importing to this to usurp testing circuit.

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