POTS Standalone Isolator Unit

The POTS Standalone Isolator Unit, Model 751222, provides 50 kV RMS (70 kV peak) of high voltage isolation between a telephone line and the drop side of one loop start telephone, dial-up modem, or loop start PBX trunk.

The unit consists of an isolator card and a power supply mounted inside a small compact enclosure. The enclosure is molded from fiberglass, making it a lightweight, flame retardant product of high dielectric strength. Its fiberglass body limits the possibility of many kinds of infiltration while providing reliable isolation from external ground potentials.

Product Number CLEI Code Description Download Documents
751222 NPMIHLAARA POTS Standalone Isolator Unit Specifications Installation Guide

Isolator Card and a Power Supply


  • Loop start PBX trunk telephone (POTS)
  • Fax and dial-up “smart” modems (up to 56.6 kb/s modem)
  • Loop start PBX
  • Dial-up remote meter reading


  • The Power Supply of the Model 751222 accepts a variety of voltage inputs with battery back-up on the Station side and provides -48 Vdc to the terminating telephone
  • CO side circuit components are powered from the CO battery feed
  • The unit’s sinusoidal ringing generator will regenerate the ring signal on the output and can ring up to five standard 500 type sets
  • The unit withstand 600 V power cross (as per UL60950) with automatic restoration of service
  • Enclosure resists the infiltration of dust, mist, and water from sprinklers
  • The unit’s operating temperature range may be extended to -4°F to 149°F (-20°C to 65°C) by removing the battery completely. If the battery is removed, in the event of a loss of service 120 Vac, there will be no back-up power provided. In this situation, the POTS Standalone Isolator Unit should be powered by a floating 48 Vdc or 130 Vdc supply)


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