Standalone Enhanced T1

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The Standalone 4-wire Enhanced T1 unit (Model 751228R2) provides high voltage isolation between an incoming 4-wire T1 carrier line and a data transmitting and receiving device located in the substation.

Note: 751228 has been manufacture discontinued and is replaced by the new enhanced T1 unit.

751228R2 is a new enhanced T1 unit. The key enhancement consists of more effective use of Surface Mount Technology (SMT) for increased reliability and greater Mean Time Between Failures (MTBF).

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

The standalone unit is shipped with an installation kit that includes a 12 conductor (6-pair) cable for connection to the Central Office (CO) incoming cable, and mounting hardware.


  • Unit is suitable for transmission at frequencies up to 5 MHz provided the data line is conditioned for operation
  • Isolation of 50 kVrms (70 kV peak) while maintaining full communication between terminals
  • Communication maintained across the gap by isolation transformers that provide low-loss low-distortion transmission
  • When not using the span power option, units do not require power input from either the CO or an external supply to operate
  • Jumper settings on the units can be configured to provide a simplex current or a loop simplex return path on the CO side. The current will not be transferred to the Station side
  • Enclosure resists the infiltration of dust, mist and water from sprinklers
Product Number CLEI Code Description Download Documents
751228R2 NPMIHLAARA Standalone 4-wire T1 Unit Specifications Installation Guide
751228SP NPMIHLAARA Standalone 4-wire T1 Unit Specifications Installation Guide


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