KR960014405B1 - Main line examination device - Google Patents

Abstract

The tester includes a plurality of switch for selecting a menu, a plurality of digital display device and light emitting display(LED), an whole surface panel unit(10) having jack and mediating element, a ventilating motor fan for preventing damage of circuit element, a back surface panel unit(20) having a switch for common power, a central controlling means(60) for controlling total operation and supporting operation for display and special menu selection, a telephone call channel(30), a digital level measuring means(50), a digital multiple measuring means(80), a power supplying means(90), and a ring signal generating menu(40).

Description

Dedicated Line Tester

1 is a schematic configuration block diagram of a dedicated line tester according to the present invention.

Figure 2 is a block diagram showing the configuration of an embodiment of a digital multiple measurement unit according to the present invention.

3 is a block diagram showing an embodiment of a call path unit according to the present invention.

Figure 4 is a block diagram showing an embodiment configuration of a digital level measuring unit according to the present invention.

Figure 5 is a block diagram showing an embodiment configuration of a multi-oscillator unit according to the present invention.

* Explanation of symbols for main parts of the drawings

10: front panel portion 20: rear panel portion

30: call path 40: ring signal generation unit

50: digital level measuring unit 60: central control unit (MPU)

70: multiple oscillation unit 80: digital multiple measurement unit

90: power supply

The present invention relates to a dedicated line tester, and more particularly, to a dedicated line tester that can measure various types of measurement items with a single device by collecting various measurement and additional functions.

Since conventional line measuring instruments exist separately for each measuring item, various measuring instruments for the line to be measured should be provided, and among these, the measuring instruments are very difficult to carry and not at all. In addition, it is very inconvenient to use, holding price is too expensive, management is also very difficult, and the measurement method is complicated, the use is very inconvenient.

Accordingly, the present invention has been made in order to solve the above-mentioned conventional problems, it is easy to use, and when measuring the line accommodated in various transmission equipment, to provide compatibility for various measurement items, and also to facilitate transport Its purpose is to provide a dedicated line tester that can be used in a narrow space and facilitates its handling, thereby reducing the complexity of the test procedure and at the same time obtaining accurate measurement values.

In order to achieve the above object, the present invention provides a dedicated circuit tester for measuring a dedicated line test having various kinds of measurement items with a single device, and includes a plurality of switches for selecting a menu to be measured. A front panel unit having a plurality of digital display and light emitting device (LED) for displaying and outputting the measurement result, a jack for connecting a test target code, and a reference value adjusting terminal; A rear panel unit including a ventilation motor fan (PAN) for preventing damage to a circuit element due to a temperature rise and a switch for inputting commercial power; Central control means for controlling overall operation of the peripheral circuits and supporting operations for various displays and specific menu selections; It is connected to the central control means and the front panel, and has 2-wire ring signal (R / D) (20 Hz) and 2-wire loop (LOOP), 2-wire ground signal (E / M) and 4-wire ground signal. A communication path means configured to support a call by supporting the (E / M) method and a dial pulse and an MFC signal (DP / MFC) method; Digital level measuring means connected to said central control means and to a front panel portion for measuring a level signal of a predetermined range with a small measuring error within a predetermined measuring frequency range; Digital multi-measurement means connected to the central control means and the front panel, performing measurement according to a predetermined measurement item and measurement range from an input signal, and converting the measurement result value into a digital value; Multiple oscillation means connected to the central control means and the front panel, generating a plurality of different frequencies, and having a predetermined output level variable range; Power supply means connected to each of the means for supplying necessary power; And ring signal generation means for generating power by receiving power from the internal power supply means and outputting a ring signal.

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

1 is a schematic structural block diagram of a dedicated line tester according to the present invention. In the drawing, 10 is a front panel unit, 20 is a rear panel unit, 30 is a call path unit, 40 is a ring signal generator, 50 is a digital level measurement unit, 60 is a central control unit (MPU), 70 is a multiple oscillation unit, 80 Is a digital multi-measurement unit, and 90 is an advanced power supply unit.

As shown in the figure, the dedicated line tester according to the present invention, the front panel unit 10, the rear panel unit 20, the central control unit 60 (hereinafter simply referred to as MPU), the communication path unit 30 and the digital A level measuring unit 50, a digital multiple measuring unit 80, a multiple oscillation unit 70, a power supply unit 90 and a ring signal generator 40 are provided.

In addition, the front panel unit 10 is provided with a jack for connecting at least four test codes, and a plurality of switches and push buttons to easily select a menu to be measured by the test operator and the measurement results There are a number of digital indicators for display output and light emitting lamps (LED) indicating the operation status of each circuit and reference value adjustment terminals, respectively, and when the test operator presses a switch or pushbutton on a menu to be measured, the input status Is applied to the multiple oscillator 70, the digital level measurement unit 50, the digital multiple measurement unit 80 and the central control unit (MPU) 60, and displays and outputs the function so that the operator can recognize the measurement result. Perform.

In addition, the rear panel unit 20 has a ventilation motor fan (FAN), a commercial power input selection switch (AC 100V / AC 220V), a fuse, and an on / off switch for preventing damage to a circuit element due to a temperature rise. ON / OFF).

The call path unit 30 is connected to the central control unit 60, the ring signal generation unit 40 and the front panel unit 10, and the two-wire ring signal (R / D) (20 Hz) type and two-wire The loop (LOOP) method, the 2-wire ground signal (E / M) method and the 4-wire ground signal (E / M) method, and the dial pulse and MFC signal (DP / MFC) methods are supported to make a call. For example, the test operator inserts the handset cord into the jack (TEL SET) of the front panel unit 10 and connects the call line to the front panel jack (4W / 2W) using the test cord of the front panel unit 10. When the call push button (TALK) is pressed, the corresponding indicator lights and the call is made. In addition, the 20Hz ring signal is transmitted, while the corresponding indicator lamp is turned on while the corresponding push button (R / D) is pressed, the ring signal is transmitted from the internal 20Hz oscillator, and the ring signal received from the other subscriber is applied to the monitor speaker. The tester can listen to the general telephone ringing sound, and at this time, the corresponding display lamp (CALL LED) of the front panel unit 10 lights up at the same time so that the tester can recognize the reception request, and the call push button (TALK) When pressed, the corresponding indicator lamp turns off and the speaker sound is stopped to allow a call test with the other subscriber. Dial pulse signal and MFC signal transmission are selected by the corresponding push button (DP / MFC), and the push button is pressed once to switch to dial pulse (DP) method and also to press MFC method. Etc. When selecting dial pulse signal method, it can select and send by LOOP signal and E (Ground signal from other party) / M (Ground signal to other party) signal. In this case, push button (L / EM) The method of selecting the push button L / EM is the same as the method of selecting the DP / MFC push button. After the selection is completed, if a random number is pressed with a dial button (KEY PAD) on the front panel unit 10, a loop (LOOP) dial pulse or an M line grounding control is transmitted. The MFC signal selection transmission is the same as the dial pulse signal method.

The ring signal generator 40 receives power from the internal power supply unit 90 and outputs a predetermined ring signal. For example, the ring signal generator 40 may have a built-in small AC ringer circuit when the test operator pushes the push button R / D of the front panel unit 10 when the test operator sends a ring signal to the other subscriber. Transmits a 20 Hz ring signal.

The digital level measuring unit 50 is connected to the central control unit 60 and the front panel unit 10 to measure a measurement level in a predetermined range with a small measurement error within a predetermined measurement frequency range. For example, the digital level measuring unit 50 is connected to a corresponding jack (LM IN) of the front panel unit 10 using a test code on a line that a test operator wants to measure, and then inputs an input impedance of 500 ohms. If you select high by using push-buffer (HI / 600), the corresponding display lamp of HI or 600 ohms is turned on and the level signal of the measuring line drawn into the test code is transferred to the internal circuit. The input levels are compared, and the level signals corresponding to the compared differences are converted into digital signals and displayed on the digital display window.

The central control unit (MPU) 60 is responsible for the overall operation control of the peripheral circuit, and when the test operator selects a front panel pushbutton or switch, and displays the result with the corresponding display lamp, the call path unit 30 In addition, the digital level measurement unit 50, the multiple oscillator 70, and the digital multiple measurement unit 80 perform a function of resource processing.

The multiple oscillator 70 is connected to the central controller 60 and the front panel 910 and generates a plurality of different frequencies, and has a predetermined output level variable range. For example, the multi-oscillator 70, 300Hz, 420Hz, 600Hz, 820Hz, 1004Hz, 2040Hz, 2400Hz, 2800Hz, 3000Hz, as the test operator presses the corresponding push button (SEL) of the front panel unit once And 3600Hz sequentially selected, and if pressed continuously, the predetermined frequency of step 10 described above is sequentially selected, and the corresponding indication lamp is turned on at the same time so that the test operator can recognize it.

Thus, when the test operator presses the selection pushbutton SEL of the front panel unit 10 to select the desired output level, impedance matching is performed so that the test operator outputs to the corresponding test code jack of the front panel unit 10. In addition, when the test push button (SEL) of the front panel unit 10 is pressed, the output level value is displayed on the digital display window of the level measuring unit so that the test operator can check its output level.

The digital multi-measurement unit 80 is connected to the central control unit 60 and the front panel unit 10 and performs measurement according to a measurement item and a measurement range determined from an input signal, and digitally measures the measurement result. Convert it to a value and print it out. For example, the digital multi-measurement unit 80 connects the line to be measured by the test operator directly to the front panel + and-terminals to measure the items (DC voltage, AC voltage, DC current, AC current, resistance, etc.). When the selection switch is pressed, measurement is performed according to the specified measurement item and measurement range and the measured result is displayed on the digital display window.

The power supply unit 90 is connected to the respective parts to supply the necessary power, the incoming voltage is AC 110 / AC commercial power applied via a power input plug jack and a protective fuse provided in the rear panel unit 20 Determined by AC220 selector switch, the incoming AC commercial power supply is applied to the internal transformer and dropped to AC 18V, then pulsated by the bridge rectifier circuit and the smoothing circuit, and it is DC + 5V, DC -5V, DC + 12V, DC -12V Output each of them.

Dedicated line tester of the present invention is configured as described above, so that it is possible to accurately measure a variety of measurement items with a single device, the dedicated according to the present invention with reference to the accompanying drawings 2 and 5 One embodiment configuration of the circuit tester will be described in more detail.

2 is a block diagram schematically showing the configuration of an embodiment of a digital multi-measurement unit according to the present invention. As shown in the drawing, a measurement range and a function selection unit 21 are connected to a measurement range and a function selection unit therebetween. An analog / digital conversion connected to an AC / DC converter 22 and a resistance value converter 23, and an input / output terminal of the measurement range and function selection unit, and converts an analog signal input for digital display into a digital signal and outputs the digital signal. And a display section 25 connected to the other output terminal of the measurement range and function selection section and the analog / digital conversion section 24 and outputting a measurement result as a digital value. It operates by receiving voltages of + 5V, -5V, + 12V, and -12V output from the power supply unit 90.

The measurement range and function selector 21 selects a DC (V) or AC (V) switch for the line to be measured and sets the appropriate measurement range (2V, 20V, 200V, 2000V). In this case, the test cord terminal is connected in parallel to the EUT, and if the measured voltage is DC (DC (V)), the + side of the tester must be connected to the + side of the measured voltage, and the-side is connected to the ground. It does not matter if the voltage being measured is alternating current (AC (V)). Measure the current value by selecting the DC (mA) or AC (mA) switch and set it to the appropriate measurement range (2mA, 20mA, 200mA, 2A). Select from high range to low range, with the test cord terminals in series with the EUT. After selecting the switch, measure the resistance and set it to the proper measuring range (2kΩ, 20kΩ, 200kΩ, 2MkΩ) .In this case, the test code terminal is connected in parallel to the measured object, and the measurement result value is displayed as 0.000. It is a short or non-resistance state of the object under test.

When the AC / DC converter 22 selects an AC current when the test operator presses the AC current measurement pushbutton AC (mA) on the front panel unit 10, AC is applied from the object to be measured. This function amplifies and converts the current using the internal rectification and conversion circuit to display on the digital display window.

The resistance value converting unit 23 selects a resistance measurement function by a test operator pressing the resistance measurement selection pushbutton (kΩ) on the front panel unit 10, and then selects an appropriate measurement range (2kΩm, 20kΩm, 200kΩm, and 2MΩ). In the case of switching to any one, a conversion function for obtaining a resistance value to be obtained by comparing a signal input from the object under measurement with a voltage value divided by the selected reference resistance value is performed.

The analog / digital converter 24 converts and outputs an analog measurement value to a digital value so that a test operator can read the measured value accurately, that is, display it on a digital display window of the front panel unit 10. Do this.

The display unit 25 is a digital display window provided on the top of the front panel unit 10 to provide a test operator with accuracy and convenience in reading.

3 is a block diagram schematically showing the configuration of an embodiment of a call path according to the present invention, which is connected to an interface 31 connected to an output of the ring signal generator 40, and connected to the interface and a known telephone set. A telephone circuit section 32, a keypad 33 connected to the telephone circuit section, a two-wire / four-wire switch 34 connected to the interface section and the telephone circuit section, and an input / output terminal of the interface section connected to the telephone circuit section. A monitor switch 35 for switching a switch connected to the switch, a ring signal switch 36 for switching a switch connected between the ring signal generator and the interface unit, and a switch and a speaker switched by the monitor switch 35. A monitor amplification unit 37 connected to the monitor unit, and a ring signal detection unit 38 connected to the interface unit and detecting a ring signal to drive a buzzer and a call lamp. The parts are operated by receiving voltages of + 5V, + 12V, -12V, and + 24V output from the power supply unit 90, and each function selection can be selected by a push button installed in the front panel unit 10. Types include 2W / 4W, torque (TALK), monitor, E / M signal, DP / MFC dial, R / D 16Hz transmission, and M / C transmission function. In addition, two types of codes may be used for the multi-jack, which is a connection terminal, and the status display uses a small display lamp (LED), and a reference value generating terminal and a handset connection jack are provided.

The interface unit 31 performs a function of shearing a ring signal when the test operator connects the test code to the corresponding jack 4WS / 2W of the front panel unit 10.

The telephone circuit unit 32, when the test operator connects the handset cord to the corresponding jack (TEL SET) of the front panel unit 10 and presses the call push button (TALK), the call tone of the target subscriber line is changed to the test code front panel jack ( 4WS / 2W, 4WR) to be delivered to the test operator so that the call can be connected.

The keypad 33 is attached to the front panel unit 10 so that a test operator can dial, and if a random number is pressed, the keypad 33 transmits a corresponding frequency or dial pulse.

The two-wire and four-wire switch 34 allows the test operator to select the corresponding subscriber line type. When the corresponding front panel pushbutton (2W / 4W) is pressed once, the circuit is connected in two-wire mode and at the same time, the corresponding display lamp. Make sure that (LED) is turned on and press it again to connect the circuit in 4 wires and at the same time turn on the corresponding indicator lamp (LED).

The monitor switch 35 allows a test operator to monitor a call and a signal state through a speaker located in the rear panel unit 10. The monitor switch 35 controls the corresponding push button MON of the front panel unit 10. Press to turn on the corresponding indicator lamp.

The ring signal switch 36 allows a test operator to transmit a ring signal. When the corresponding push button R / D of the front panel unit 10 is pressed, the ring signal switch 36 transmits 20 Hz to the other subscriber. Generate and send a ring signal.

The monitor amplifying unit 37 amplifies a signal applied from the interface and transmits the signal to the speaker attached to the rear panel unit 20, wherein the speaker sound is adjusted to the volume provided in the front panel unit 10. So that it can be monitored at an appropriate size.

The ring signal detector 38 detects the ring signal applied from the other subscriber and drives the buzzer and the call lamp connected to the rear stage.

4 is a block diagram schematically showing the configuration of an embodiment of the digital level measurement unit according to the present invention. The HI / 600 selector switch 41, which selects the terminal impedance high or 600? A low pass filter 42 for filtering the input signal, an attenuator 43 connected to the low pass filter, an amplifier 44 connected to the attenuator, rectifier 45 connected to the amplifier, and the rectifier And an AC / DC converter 46 connected to the AC controller, a cover control module 47 connected to the AC / DC converter, and a digital display 43 connected to the display control module.

When the HI / 600 selector switch 41 pushes the push button HI / 600 provided on the front panel unit 10 once, a green indicator lamp is turned on and a circuit is opened to correspond to the front panel unit 10. Terminating the input to (LM IN) with a high (HI), and if pressed once again is switched to operate as a 600Ω termination circuit, at this time, the red display lamp provided in the front panel unit 10 is turned on.

The low pass filter 42 cuts out a high frequency outside the frequency range of 300 Hz to 3600 Hz when the signal from the circuit under measurement is applied through the jack LM IN positioned in the front panel unit 10. Perform the filtering function.

The retarder 43 performs a function of appropriately attenuating the signal level applied from the low pass filter 42 to a signal of +10 dB to -40 dB, which is a measurement level tolerance.

The amplifier 44 performs a function of amplifying and outputting a signal popular from the attenuator 43 so as to be displayed on the digital display unit 48 at the rear stage.

The rectifier 45 performs a function of removing the pulse flow characteristic of the amplified signal applied from the amplifier 44 through the rectifier circuit.

The AC / DC converter 46 performs a function of converting and outputting a signal level from which the pulse flow characteristic component outputted from the rectifier 45 is removed into a DC signal.

The display control module unit 47 controls the signal level applied from the AC / DC converter 46 to be displayed numerically on the digital display unit 48 located in the front panel unit 10. .

The digital display unit 48 is positioned at the upper end of the front panel unit 10 to provide convenience for the test operator to read, and accurately displays the result of the measurement on the digital display window.

As described above, the measurement frequency range of the digital level measurement unit according to the present embodiment is 300 Hz to 3600 Hz, the measurement level range is +10 dB to -40 dB, the measurement error is within ± 0.5 dB, and the input impedance is 600 ohm ± 15%. High / high (HI) is over 8Kohm.

5 is a block diagram schematically showing an embodiment configuration of the multi-oscillator unit according to the present invention, the frequency generating the frequencies of 300Hz, 420Hz, 600Hz, 820Hz, 1004Hz, 2040Hz, 2400Hz, 3000Hz, and 3600Hz, respectively An analog multiplexer unit 52 connected to the output unit 51 and an output terminal of the frequency generator unit; an amplifier 53 connected to an output terminal of the analog multiplexer unit and amplifying and outputting an input signal; and an output terminal thereof to the analog multiplexer unit. The connected digital logic unit 55, and a selection switch 54 having an output terminal connected to the digital logic unit, and a frequency display unit 56 connected to an output terminal of the digital logic unit are provided.

The frequency generator 51 generates 300Hz, 420Hz, 600Hz, 820Hz, 1004Hz, 2040Hz, 2400Hz, 3000Hz, and 3600Hz and outputs the frequencies to the analog multiplexer 52.

The analog multiplexer unit 52 selects and outputs a desired frequency signal according to the control of the digital logic unit 55 among various frequencies applied from the frequency generator 51.

The amplifier 53 amplifies and impedance-matches the frequency signal applied from the analog multiplexer 52 and outputs it to a corresponding jack (OSC OUT) located in the front panel unit 10, the internal variable resistor ( VR) to adjust the output level.

The selection switch 54 performs a function of allowing a test operator to select any one of the frequencies output from the analog multiplexer unit 52 from the frequency generator 51. In the front panel unit 10 is arranged as a selection push button (SEL) to be changed by one step when the test operator presses each time, so that the corresponding frequency display lamps provided in the front panel unit 10 is turned on Allow the operator to select the desired frequency. If you press and hold, the frequencies are selected sequentially in the order of 10 steps.

The digital logic unit 55 controls a frequency signal selected by the test operator through the selection switch 54 to be selected by the analog multiplexer unit 52, and the corresponding frequency display lamp provided in the front panel unit 10 is Output a control signal to turn on. In addition, when the test operator presses the push button (TST) provided in the front panel unit 10 to check its generated frequency output level, the frequency output level is displayed on the digital display window provided in the front panel unit 10. It also performs a function to control it.

The frequency display unit 56 includes a plurality of display lamps positioned in the front panel unit 10, and a frequency selected by the test operator through the selection switch 54 under the control of the digital logic unit 55. The frequency display lamp corresponding to the lamp is turned on so that the test operator can recognize it.

In this embodiment, the frequency generation accuracy of the frequency generator is within 1 Hz of the reference, the output level variable range is 2dBm ~ 30dBm, the output impedance is within 600ohm ± 20%.

Thus, the dedicated line tester of the present invention, the operation of the level meter function to perform the extension test to test the HI / 600 switch in the HI position, and the segment test to test the HI / 600 switch in the 600, and oscillator function 2-wire loop (2W LOOP), 2-wire ground signal (2W E / M), 4-wire ground signal (2W E / M), 2-wire ring signal (2W R) / D) and MFC (4W / 2W common) operation and digital multi-tester function, such as resistance measurement, voltage measurement, current measurement, etc. can be operated easily and smoothly.

Accordingly, the present invention, which is configured and operated as described above, collects various measurement and additional functions to measure various types of measurement items with a single device, thereby improving measuring device management and utilization, and It is possible to easily obtain all the accurate measured values and to make complex track facility management efficient.

Claims (5)

In a dedicated line tester that can measure a dedicated line test having various kinds of measurement items with a single device, it is equipped with a plurality of switches to select a menu to be measured and a plurality of switches for displaying and outputting the measurement results. A front panel unit 10 having a digital display and a light emitting element (LED), a jack to which a test target cord can be connected, and a reference value adjusting terminal; Ventilation motor fan (FAN) to prevent damage to the circuit elements due to the temperature rise, and the rear panel unit 20 is provided with a switch for commercial power input; Central control means (60) which is in charge of the overall operation control of the peripheral circuit and supports the operation for various displays and specific menu selection; It is connected to the central control means 60 and the front panel unit 10, and has a 2-wire ring signal (R / D) (20 Hz) method, 2-wire loop (LOOP) method, 2-wire ground signal (E / M). A call path means 30 configured to support a call, a 4-wire ground signal (E / M) method, a dial pulse and an MFC signal (DP / MFC) method; Digital level measuring means (50) connected to said central control means and to a front panel portion for measuring a level signal of a predetermined range with a small measuring error within a predetermined measuring frequency range; A digital multi-measurement means (80) connected to the central control means and the front panel, for performing a measurement according to a predetermined measurement item and a measurement range from an input signal, and converting the measurement result value into a digital value; A multiple oscillation means (70) connected to the control means and the front panel at the center and generating a plurality of different frequencies and having a predetermined output level variable range; Power supply means (90) connected to the respective means for supplying necessary power; And ring signal generating means (40) for receiving power from the internal power supply means to generate and output a ring signal. The method of claim 1, wherein the digital multiplex measurement means (80) selects a direct current voltage (DC (V)) or an alternating voltage (AC (V)) for a voltage measurement for a line to be measured, and then selects a suitable measurement range. To measure the current value, select DC current (DC (mA)) or AC current (AC (mA)) and set it to the proper measuring range, but in order from high range to low range to eliminate the concern of over current. A measurement range and function selection means 21 for selecting a function and for measuring the resistance value so as to select a function and then adjust it to a suitable specific range; AC / DC conversion means 22, connected to the measurement range and function selection means, for amplifying and converting an AC current applied from the object to be measured using an internal rectification and conversion circuit; Connected to the measurement range and function selection means, and when the test operator selects a resistance measurement function and then selects a suitable measurement range, the voltage divided by the measured value and the selected reference resistance value for the signal input from the measured object Resistance value converting means (23) for comparing and using the values to obtain and output a resistance value; An analog / digital conversion means (24) connected to an output end of the measurement range and function selection means, for converting an input analog signal into a digital signal and outputting the digital signal so that a test operator can read the measurement value accurately; And display means (25) connected to the output range of the measurement range and function selection means and the analog / digital conversion means (24) and outputting the measurement results as digital values. Dedicated line tester. The method of claim 1, wherein the communication path means 30 is connected to the output terminal of the ring signal generating means 40, the test operator to transmit the test code to the corresponding jack (4WS / 2W) of the front panel portion 10 Interface means (31) which, when connected to, transmits a ring signal; When the test operator connects the handset cord to the corresponding jack (TEL SET) of the front panel unit 10 and presses the call push button (TALK), the test tone of the target subscriber line is connected to the test code front panel jack. A telephone circuit 32 which is delivered to the test operator via 4WS / 2W and 4WR to allow a call to be connected; A keypad 33 connected to the telephone circuit and attached to the front panel unit 10 so that a test operator can dial; A two-wire and four-wire switch 34 connected to the interface means and the telephone circuit and allowing the test operator to select according to the target subscriber line type; A monitor switch 35 connected to the telephone circuit so that a test operator can monitor a call and a signal state through a speaker located in the rear panel unit 10; A ring signal switch (36) for switching a switch connected between said ring signal generating means and said interface means so that a test operator can transmit a ring signal; Amplifying means (37) for amplifying a signal applied from the interface means and transmitting the amplified signal to a speaker located in the rear panel unit (20); And ring signal detecting means (38) connected to said interface means for detecting a ring signal applied from a counterpart subscriber. 2. The apparatus of claim 1, wherein the digital level measuring means (50) comprises: selecting means (41) for selecting a terminal impedance of high or 600 ohms according to a test operator's selection; Low-pass filter means 42 for blocking and filtering high frequencies outside a predetermined measurement frequency range when a signal from a line under measurement is applied; Attenuation means (43) for attenuating the signal applied from said low pass filter means (42) within a measurement level tolerance; Amplifying means (44) for amplifying and outputting a signal applied from the attenuation means (43); Rectifying means (45) for removing the pulsating characteristics of the amplified signal applied from the amplifying means (44); Alternating current / direct current converting means (46) for converting and outputting a signal level from which the pulse flow characteristic component outputted from the rectifying means (45) is removed into a DC signal; Display control means (47) for controlling a signal level applied from said AC / DC conversion means (46) to be displayed as a digital value; And a digital display means 43, connected to the display control means, positioned at an upper end of the front panel portion 10 for easy reading by a test operator, and displaying a measured value on a digital display window. Dedicated line tester, characterized in that. 2. The apparatus of claim 1, wherein the multiple oscillation means (70) comprises: frequency generating means (51) for generating and outputting a plurality of different frequencies; An analog multiplexing means (52) for selecting and outputting a desired frequency signal under the control of the digital logic unit (550) among a plurality of frequencies applied from the frequency generating means (51); An amplification means 53 configured to output by amplifying and impedance matching, and to adjust an output level; any one of frequencies applied by the test operator to the frequency output from the analog multiplexing means 52; A selection input means (54) to select an analogue output, the output terminal being connected to the analog multiplexing means, such that a frequency signal selected by the test operator through the selection input means (54) is selected by the analog multiplexing means (52); Digital logic means 55 for controlling and the digital It is connected to the output of the logic means, and has a frequency display means 56 for the test operator to recognize the test operator by lighting the frequency display lamp corresponding to the frequency selected by the test operator through the selection input means (54) Dedicated line tester, characterized in that.