72 TX3 Telephone Access System Installation and Operation Manual Version 5.4
LT-969 Copyright 2019
NSL Relay Cabinet Installation and Wiring
5.2 NSL Relay Control Unit and Expanders
The TX3-NSL-8M NSL Relay Control Unit, TX3-8EC and TX3-16EC NSL
Relay Backplane Expanders perform the following functions:
• Telephone switching functionality to facilitate voice communication
between the resident's phone and the lobby
• Generating call waiting tones to the resident if the line is busy.
• Provide access control by the resident using the telephone keypad.
• Low power operation from one 16V AC transformer.
5.2.1 TX3-NSL-8M NSL Control Unit
The TX3-NSL-8M Relay Control Unit consists of:
• NSL Main Controller Board
• NSL Backplane Board
Figure 41 shows a TX3-NSL-8M Relay Control Unit.
Figure 41. TX3-NSL-8M Relay Control Unit
TX3-NSL-8M Relay Control Unit
NSL Main Controller
NSL Backplane Board