RDL ST-TC1 Telephone System Coupler CO Line Simulator

Add dependable paging and radio-control capability to your on-site telephone system with the Radio Design Labs ST-TC1 Telephone System Coupler. Designed to simulate a CO line into a KSU or telephone switching unit, the ST-TC1 provides a maintained relay contact closure when the line is seized — instantly activating paging, radio, or other response equipment for security, surveillance, and monitoring applications. A 600 Ω transformer-isolated audio feed delivers clean audio input/output to the switching unit and the unit reliably passes DTMF tones for keypad-controlled access. The ST-TC1 is AC-powered and intended for connection only to telephone switching equipment (not to live CO lines or lines with ringer voltage), simplifying installation while protecting your telecom infrastructure. For two-way radio or intercom integrations, pair the ST-TC1 with RDL ST-VOX1 modules to provide push-to-talk keying and full duplex control. If you need to expand paging zones, interface radios to your phone system, or add emergency monitoring triggers, the ST-TC1 offers a compact, purpose-built solution—contact us to discuss integration into your security or paging system.

• Seamlessly add paging or radio control to an on-site KSU without a dedicated CO line
• Provides a maintained relay contact closure when the simulated line is seized to trigger paging or security systems
• 600 Ω transformer-isolated audio feed for clean, isolated input/output to telephone switching units
• Passes DTMF tones for keypad-controlled paging or system access and works with ST-VOX1 for two-way radio keying
• AC-powered, US-made hardware built for reliable integration into security, surveillance, and monitoring installations