Holding Coil

The Holding Coil Unit, Model 7501-40, is used in conjunction with various Teleline Isolator cards for four-wire DX signalling applications (four-wire simplex DC current), as well as for DC simplex powering requirements (i.e., carrier). This type of signalling, also used by certain PBX tie-lines, is fully described in the installation guide.

Applications:

• 4-wire DX signalling
• DC simplex powering

Features:

• The unit provides a means of reintroducing DC voltage across the TX and RX pairs of isolated DX signals
• The unit is bi-directional and, therefore, the DC voltage source can originate from the Station or CO side
• The unit can be used to power a two-wire circuit from the Tip & Ring, using an external power supply