Loop a Line consists of an OSCILLATOR or TONE SENDER and a SIGNALLING PROBE. Two sets of test leads complete the equipment.
The service technician connects the Oscillator to the cable pair at the exchange MDF or street cabinet. The Oscillator starts in the 'TONE' mode allowing the technician to identify the pair at the Far End of the Line with the Probe. Several different Tones are selectable allowing multiple Oscillators to operate on the cable.
After pair identification, the Probe leads may be connected to the pair and the Oscillator signalled by pressing 'OPEN' or 'SHORT' buttons, to allow foreign battery, insulation resistance, loop resistance and resistance balance checks as well as fault finding using a TDR or Resistance Bridge. After repair or installation, a final press of the 'CONNECT EXCHANGE' button restores the customer's service to provide dial or ring-back checks.