4-wire AC Data Standalone Isolator Unit

The 4-wire Data Standalone Isolator Unit, Model 7501-53, provides high voltage isolation between an exterior dedicated four-wire data line and data transmitting / receiving equipment located inside the substation.

The installation kit consists of an isolator card mounted inside a compact enclosure, a cable, and mounting hardware. The enclosure is molded from fiberglass, making it a lightweight, flame retardant container of high dielectric strength. Its fiberglass body limits the possibility of many kinds of infiltration while providing reliable isolation from external ground potentials.

The standalone unit is shipped with a 10’ PVC insulated 6-pair CMAW cable for connection to the CO’s incoming cable.

Product Number CLEI Number Description Download Documents
7501-53 NPMWT202RA 4-wire Data Standalone Isolator Unit Specifications Installation Guide

4-wire AC Data Standalone Isolator Unit


  • Dedicated 4-wire line modems
  • Analog Supervisory Control and Data Acquisition (SCADA) systems
  • Tone relay control systems (Teleprotection)
  • Analog carrier systems
  • Digital Data Service (Ex: 56K DDS Networking)
  • Any other equipment using tone-related signalling


  • The unit provides isolation of 50kV RMS (70kV peak) while maintaining full communication up to 64 kbps for a 4-wire dedicated data circuit
  • The unit is suitable for transmission at frequencies of up to 200 kHz provided the data line is conditioned for operation at this speed
  • The unit does not require power input from either the CO or an external supply to operate
  • The unit permits the flow of CO simplex sealing current from one pair to another. Simplex sealing current is not transmitted across the isolation gap to the Station side
  • The enclosure resists the infiltration of dust, mist, and water from sprinklers