Key System US Atlas IIE KSX 32i, Installation Manual

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Main Control Board (MCB) Refer to Figure 2.
4.05. The MCB is the main controller card of the system. It performs all logical operations,
call processing, and uses control signals to control the other cards in accordance
with system demands.
4.06. The MCB uses a 20 MHz 16 bit 80C188XL micro-processor and has a memory
capacity of 256Kb of ROM, and 128 Kb of RAM. The system uses a 24 MHz
oscillator.
4.07. The system control software is in a 256 Kb EPROM (2 Mbit), which can be
upgraded, and the stored-program database is in battery-protected RAM.
4.08. The following are located on the MCB (refer to Figure 2):
A) Memory battery protection and disconnect switch.
B) Terminal block for external connections to Loud Bell, Page, Page Relay, and
External Music Source.
C) Ribbon cable connector to SMDR Unit.
D) Switch to select Music source (internal or external)
E) LED's indicating system operation and memory backup.
F) 8 element DIP switch for hardware programming.
G) Modular Jack for connection to external Door Phone control unit.