TX 120
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General

The TX120A is a low cost, multi-function test instrument, primarily for determining the suitability of twisted copper pairs for use by Pair Gain Systems, ISDN and HDSL but with application in the testing of such pairs for normal telephone services.

In many cases, the TX120A eliminates the need for expensive instruments such as Pulse Echo Testers (PETs) and Transmission Testers.

Loading coils, build-out capacitors and surge protection devices are necessary components of many POTS lines. Bridged taps, split pairs, poor joints and leaky insulation are conditions that are undesirable but often tolerated on POTS lines. However, all of these conditions seriously affect the operation of high frequency systems and must, therefore, be found and eliminated or corrected before such systems can be installed.

The TX120A consists of three main components. The SENDER is connected to one end of the line at the exchange, pillar or pit. The RECEIVER is connected to the other end of the line and displays all test results and controls the function of the SENDER. The PROBE is used, if necessary, to identify the pair under test.

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Function

Exchange Connection and Disconnection.

• Pair Identification.
• Line Insertion Loss measurement @ 820Hz and 3kHz.
• Line Insertion Loss measurement @ 40kHz, 100kHz and 150kHz.
• Noise measurement (continuous and peak capture).
• Line Looping (used for PET distance calibration and for Varley bridge fault location).
• Loop Resistance measurement.
• Line Isolation (used for testing with other instruments).
• Foreign Battery measurement (A-B, A-GND and B-GND) and Line Voltage measurement.
• Line Balance measurement.
• Insulation Resistance measurement (A-B, A-GND and B-GND).

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Features

• Incorporates the features of the well known Teletech TX90 Loop-a-Line and TX95 Line Disconnect Accessory.
• Uses the same, robust low frequency signalling method as used in Loop-a-Line.
• SENDER and RECEIVER have remaining battery indication in hours.
• SENDER and RECEIVER have a two line by 16 character LCD display for test results and status messages.
• When being used in an exchange, the SENDER can be powered from the exchange battery.
• The RECEIVER has terminals for the connection of other instruments to the line.
• Powered by easily obtainable 9V alkaline batteries.
• Busies the line to incoming calls during testing.
• To conserve battery energy, the Receiver automatically powers down if inactive for more than two minutes.
• The warble rate of the pair identify tone is variable so that up to three SENDERS can be used simultaneously on different lines.
• SENDERS are addressable so that up to three can be used simultaneously on the same line.

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Technical

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