RDL ST-TC1 – Telephone System Coupler, CO Line Simulator

What is the RDL ST-TC1?

The RDL ST-TC1 is a telephone system coupler that simulates a CO line so an on-site telephone switching unit (KSU) can control paging or radio systems. It connects to the KSU as if it were an incoming phone line.

How does it work?

When the KSU seizes the line to the ST-TC1, a relay contact closure is held for as long as the line is seized, which can switch a paging system or radio system. A 600 Ω transformer-isolated audio feed carries audio into or out of the telephone switching unit, and DTMF tones pass through. The ST-TC1 is not intended for connection directly to a telephone CO line or to any line with ringer voltage present. RDL notes it can be paired with the RDL ST-VOX1 to provide push-to-talk for two-way communications.

What are the key features?

• CO line simulation — The module appears to the KSU as an incoming phone line for adding paging zones or radio interfaces.
• Relay closure on line seizure — Relay contacts close when any extension seizes the line and stay closed while it is held.
• Transformer-isolated audio — A 600 Ω isolated audio feed passes audio to or from the telephone switching unit.
• DTMF pass-through — DTMF tones from a telephone keypad or other generator pass through the module.
• Two-way radio interface — Pairing with an ST-VOX1 adds push-to-talk keying for two-way systems.