4 WAY ISOLATION PCB
Description :-
One PCB required for every four handsets.•
Isolates the speech, lock and call lines with the use of relays.•
protects the +12v supply and door monitoring line with fuses.•
There are LED's on the isolation PCB to indicate which phone has been•
enabled.
All connections are via plugs.•
Operation :-
The selects from the call buttons all go to a separate outputs on JP6 (either
A,B,C or D). When one of these outputs goes high (i.e. with a call to that
output), a thyristor on the isolation PCB is triggered, which in turn energises
the relays for that handset. Each of the four outputs on the isolation PCB
have two relays which reconnects the connections on JP1 with the
connections on that phone output (either JP2, JP3, JP4 or JP5). The thyristor
is held on by the voltage on the SW+ terminal on JP1. This voltage is only
there when a call is in progress.
Technical specification
Number of users : 4
Input voltage : 12VDC
Current (Quiescent) : 0mA
Current (During call) : 47.6mA
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