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Quick Test

Quick Test X21LM  [END OF LIFE]

  • 6 four state monitors for speeds up to 10Mb
  • Distinct threshold at +/- 300 mV
  • Interface/ battery or adapter powered
  • compact and easy to read out
  • User manual, pouch for carrying
A complete X21 Line-Monitor for speeds up to 10Mb.It shows state of all lines in a glance. It can be interface, battery or mains powered - a power LED tells the class of your interface.

The X21LM tests all 6 circuits of this standard. It keeps a distinct threshold over the whole range DC-10Mb. The low power needs leaves you the choice between interface, battery or mains powering. The power LED shows the strength of your interface. Two small AA batteries power the unit over 150 hours.

The Comtest X21LM is the result of our over 15 years experience in the field building interface test equipment. Noticing many use Breakout Boxes but never the breakout system made us design the X21LM. Modern circuitry enabled us to build it this way.

In contrary to other Line Monitors (Breakout Boxes) the LEDs do not dim with increasing speed, it keeps a distinct threshold at 300mV from DC up to 10Mb. The X21LM’s low power requirement enables the interface to power it, battery powering is possible for testing extremely weak interfaces.


An interface powered X21LM comes useful testing the interface-powered mini RS232/X.21 modems. Communication quality differing between an interface and external powered X21LM can mean your mini modem needs mains powering.

The logical face plate provides complete and easy to read information. The X21LM is housed in a rigid ABS case, one battery holder with 2 AA batteries, manual and pouch for transport.

COMCRAFT — 17 rue des Frères Lumière, 67201 Eckbolsheim, France — Tel: +33 (0) 3 88 10 18 30