ABSTRACT: The Low-Speed Signaling Channel Unit (LSS CU) is a transmitting or receiving channel unit. Every 125 us, the unit accepts an input from, or delivers an output to, one of the several low-speed circuits (subchannels) connected to it. The maximum signaling speed is 30 baud. Each channel unit type allows several low-speed signaling circuits to share a channel time slot of a digital transmission system.

This Technical Reference (TR) presents the view of Telcordia on generic requirements for three types of LSS CUs:

• Open and close the loop (direct wire alarm circuit)
• Open, close, and ground the loop (McCulloh alarm systems)
• Switch the polarity of the battery that terminates the loop (polarity reversal alarm system).