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Telephone System Coupler



The ST-TC1 is intended to be connected to an on-site telephone system switching unit KSU. It is NOT intended to be connected directly to a telephone CO line. Connections from the ST-TC1 go into the telephone switching unit as if the ST-TC1 was an incoming phone line.

When the KSU seizes the line to the ST-TC1, a relay contact closure is provided which can be used to control a variety of equipment, such as a paging system or radio system. The closure is maintained as long as the line is seized. A 600 Ω transformer-isolated audio feed is available for audio input to or output from the telephone switching unit. The ST-TC1 will pass DTMF audio from a telephone keypad or other DTMF generating device.

The ST-TC1 may be utilized to add paging zones or radio system interface to a telephone system. When any instrument in the telephone system seizes the line associated with the ST-TC1, the relay closes to activate the radio or paging function, and the audio spoken into the handset is broadcast. The ST-TC1 can not be connected to a phone line that has ringer voltage present.

The ST-TC1 can be used in conjunction with RDL's® ST-VOX1 modules to provide two-way communication. The ST-VOX1 will provide the necessary push-to-talk function to key the two-way communications systems.

PS24AS power supply sold separately.

Main Features:
• Simulate a Telco CO Line
• Connect to local telephone switch or instrument
• Add Radio Control or Paging to KSU
Contact Closure when Line is Off-hook
• Audio Input/Output from Telephone Switching U


• Line Connection: Simulated telco central office line to feed telephone system
• Audio In / Out Impedance: 600 Ω balanced
• Switching Contacts: Double-pole, double-throw
• Max. Switching Power: 60 W, (220 Vdc, 125 Vac, 2 A)
• Power Requirement: GROUND-REFERENCED, 24 Vdc @ 50 mA
• Ambient Operating Environment:0° C to 55° C

RDL ST-TC1 Figure 1

RDL ST-TC1 Figure 2


RDL ST-TC1 Figure 3 

List Price: $168.09
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