KR20000002925U - Eavesdropping on the phone - Google Patents

Abstract

The present invention relates to a telephone, and in particular, by detecting the difference in voltage between the tip terminal and the ring terminal in the telephone and displaying the occupied state of the trunk line assigned to the telephone, so that other users can visually check whether the trunk line is occupied. Relates to a wiretap detection device in a telephone.

The present invention has a voltage sensing circuit between a tip terminal and a ring terminal in a telephone to measure the corresponding voltage that is constantly supplied between the tip terminal and the ring terminal according to whether the trunk line is occupied and compared with a preset comparison voltage. By displaying the trunk line occupancy state, the eavesdropping state and the use state of another telephone can be visually confirmed.

Description

Eavesdropping on the phone

The present invention relates to a telephone, and in particular, by detecting the difference in voltage between the tip terminal and the ring terminal in the telephone and displaying the occupied state of the trunk line assigned to the telephone, so that other users can visually check whether the trunk line is occupied. Relates to a wiretap detection device in a telephone.

In general, telephones are connected to each home through a telephone terminal box in many places, such as an apartment complex, when an analog trunk line is used.However, even if a user taps a call in the telephone box, the user cannot know the telephone. It is possible to connect several telephones with one CO line. In this case, when the phone is occupied by CO line, the user can check the call state by picking up the handset.

The present invention has been made in view of the above-described problems. In the telephone, a voltage sensing circuit unit is provided between the tip terminal and the ring terminal, and the voltage constantly supplied between the tip terminal and the ring terminal changes depending on whether the trunk line is occupied. The purpose of the present invention is to visually check the eavesdropping state and the state of use of another telephone by measuring the corresponding voltage and displaying the trunk line occupation state by comparing with the preset comparison voltage.

1 is a block diagram showing a telephone circuit unit according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a voltage sensing circuit unit shown in FIG. 1. FIG.

Explanation of symbols on the main parts of the drawings

10: ring detection unit 20: voltage sensing circuit unit

21: voltage comparator 21-1, 21-2: comparison means

21-3, 21-4: Display part 30: Voice call circuit part

R3, R4: Variable resistor

In order to achieve the above object, the present invention is characterized in that the telephone, having a voltage sensing circuit for detecting the voltage across the tip / ring to indicate the state of tapping and the use of the other telephone.

In addition, the voltage sensing circuit unit includes a variable resistor for variably adjusting the voltage across the tip / ring; Comparison means for comparing the operation detection voltage input through the variable resistor with a predetermined comparison voltage; And a display unit for displaying the eavesdropping state and the use state of the other telephone according to the output level of the comparing means so that the user can visually confirm.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, the telephone circuit unit according to an embodiment of the present invention detects a voltage across the tip / ring and checks a tapping state and a use state of another telephone, and a voltage sensing circuit unit 20 received from a trunk line. A ring detection unit 10 for detecting a ring signal and a voice call circuit unit 30 for connecting a call path through a microphone and a speaker are provided.

The voltage sensing circuit unit 20 includes a voltage comparing unit 21 for comparing the voltage across the tip / ring and displaying an output state, and the corresponding voltage comparing unit 21 variably adjusts the voltage across the tip / ring. (R3, R4), comparing means (21-1, 21-2) for comparing the operation sensing voltage input through the corresponding variable resistor (R3, R4) and a predetermined comparison voltage, and the corresponding comparing means 21-1 And display units 21-3 and 21-4 for displaying the eavesdropping state and the use state of the other telephones according to the output level of the present invention.

When described in detail with reference to the accompanying drawings, the operation of the present invention configured as described above as follows.

In general, when a voltage of 48V is supplied from the exchange to the subscriber and a ring signal from the exchange is detected by the ring detection unit 10 to form a call path, the user drops the voltage across the telephone when the user talks through the speaker and the microphone. For example, when several telephones simultaneously occupy a trunk line, more voltage drops are generated at both ends of the telephone than with one telephone.

First, when the telephone is not used, a voltage of 48V is supplied from the exchange between the tip and ring terminals, but the voltage between the tip and ring terminals depends on the distance between the exchange and the state of the telephone line. It is not constant.

In addition, the voltage sensing circuit unit 20 has the same first and second resistance values in order to prevent the voltage of the tip terminal and the ring terminal from changing.

In addition, since the voltage between the tip terminal and the ring terminal of the telephone is not constant depending on the distance between the switch and the state of the telephone line, the voltage input to the comparing means 21-1, 21-2 in the corresponding voltage sensing circuit section 20. The third and fourth resistance values can be variably adjusted to be equal to or greater than a predetermined voltage according to each state.

For example, adjust the values of the two variable resistors R3 and R4 so that the third resistor is 3.6KΩ and the fourth resistor is 1KΩ so that the voltage across the fourth resistor is 5V or more when the telephone is not used. The preset comparison voltages V1 and V2 of the first comparison means and the second comparison means are preset to 5V and 2.5V, respectively.

At this time, V1 is a voltage capable of confirming whether another telephone is in use when multiple phones are used, and V2 is a voltage capable of confirming whether another telephone is used by another user during a call.

Then, when the telephone is not used, the voltage sensing circuit unit 20 receives a 48 V voltage supplied between the tip terminal and the ring terminal from the exchanger, and the first and second resistance values connected in parallel between the tip terminal and the ring terminal. Since this is the same, a reference voltage of 24 V is input to the voltage comparing section 21 by voltage division.

At this time, the voltage comparing unit 21 in the voltage sensing circuit unit 20 uses a variable resistor so that it can be adjusted according to the state of the telephone line. The operation sensing voltage input to the comparing means 21-1 and 21-2 is represented by the following equation. Is calculated by.

Motion detection voltage = R1 * reference voltage / (R1 + R2)

According to Equation 1, 5.2V operation sensing voltage is input to the comparison means 21-1 and 21-2.

Accordingly, the comparison means 21-1 and 21-2 compares the input operation detection voltage with a predetermined comparison voltage V1 and V2, and detects the motion applied through the corresponding variable resistors R3 and R4. Since the voltage 5.2V is larger than the predetermined comparison voltages V1 and V2, the outputs of the corresponding comparison terminals 21-1 and 21-2 become 'high' levels, and thus the display units 21-3 and 21-4. LED is off.

On the other hand, let's take a look at the case of using the telephone through the telephone terminal box from the outside.

Similarly, the first and second resistors in the voltage sensing circuit unit 20 are the same, and the third and fourth resistors are variable resistors, respectively, 3.6 KΩ and 1 KΩ, respectively, and V1 of the comparison means 21-1 and 21-2. Is 5V and V2 is assumed to be 2.5V.

When the telephone is used through the telephone terminal box externally, the voltage between the tip terminal and the ring terminal of the telephone drops to 24V, and the voltage is divided by the first and second resistors in the voltage sensing circuit section 20 so that the reference voltage of 12V is compared. Applied to the unit 21.

Accordingly, the operation detection voltage input to the comparison means 21-1 and 21-2 in the voltage sensing circuit unit 20 becomes 2.6V by Equation 1 above.

Then, an operation detection voltage of 2.6 V is input to the first comparison means 21-1 and compared with a predetermined comparison voltage V1, since the operation detection voltage is smaller than the predetermined comparison voltage V1. The output of the first comparing means becomes 'low' level so that the LED of the first display unit is turned on.

The second comparison means 21-2 receives an operation detection voltage of 2.6 V and compares it with a predetermined comparison voltage V2, since the operation detection voltage is larger than the predetermined comparison voltage V2. The output of the second comparing means 21-2 is at the 'high' level so that the LED of the second display unit is turned off.

Therefore, if the LED of the first display unit 21-3 is turned on when the telephone is not used, it is possible to visually know that the telephone is being used from the outside.

On the other hand, a case where the telephone is intercepted from the outside through the telephone terminal box while using the phone will be described as an example.

When the phone is intercepted while using the telephone through the telephone terminal box, the voltage between the tip terminal and the ring terminal of the telephone drops below 12 V. Therefore, the voltage is reduced by the first and second resistors in the voltage sensing circuit unit 20. The reference voltage of 6V is input to the voltage comparator 21.

Accordingly, the voltage input to the comparison means 21-1 and 21-2 in the voltage comparator 21 becomes 1.3V by Equation 1 such that the corresponding operation detection voltage is smaller than the predetermined comparison voltages V1 and V2. Therefore, the outputs of the comparison means 21-1 and 21-2 are at the 'low' level, and the LEDs of the display parts 21-3 and 21-4 are turned on.

Therefore, when the phone is used, when the LEDs of the display parts 21-3 and 21-4 are turned on, it is possible to visually know that someone is tapping the phone from the outside.

As such, the phone includes a voltage sensing circuit unit 20 between the tip terminal and the ring terminal, and measures a voltage between the tip terminal and the ring terminal to which a voltage supplied with a predetermined voltage drops when the phone is used. By displaying the state in comparison with the comparison voltage, the eavesdropping state and the use state of the other telephone can be visually confirmed.

As described above, the present invention includes a voltage sensing circuit unit between the tip terminal and the ring terminal in the telephone to measure a corresponding voltage that varies depending on whether the voltage supplied constantly between the tip terminal and the ring terminal is occupied by the trunk line. By displaying the occupation state of the trunk line in comparison with the set comparison voltage, it is possible to visually check the state of tapping and use of another telephone.

Claims (2)

In the phone, Eavesdropping detection device in the telephone, characterized in that it comprises a voltage sensing circuit (20) for sensing the voltage across the tip / ring to indicate the tapping state and the use state of the other phone. The method of claim 1, The voltage sensing circuit unit 20 includes variable resistors R3 and R4 for varying the voltage across the tip / ring; Comparison means (21-1, 21-2) for comparing the operation detection voltage input through the variable resistors (R3, R4) and a predetermined comparison voltage; And display units 21-3 and 21-4 for displaying the eavesdropping state and the use state of other telephones according to the output level of the comparing means 21-1 and 21-2 so that the user can visually check. Eavesdropping detection device in the telephone.