How PSAL module works?

[mshahzadjaved]

My question is about the working of PSAL chip installed on front bottom side of M3 cabinet.
It has three wires: Input: -48V(Blue wire),Input: +48V(Red wire) and Output: -48V(Brown wire) to Power Supply module of ACT-28. The documentation says that when rectifier fails, backup batteries come in operation and voltage starts decreasing and reaches a threshold(45V) and it generates a PSAL signal to CPU to safely shutdown.
My question is What type of signal the module sends (Digital or Analog) as in normal conditions I have measured -48V on brown wire of the PSAL chip..........NOW.............When I bypass/disconnect the PSAL module and directly connects the -48V to ACT-28 Power supply module PSAL terminal(brown wire) the system works normal and in this condition I assume that when rectifiers will fail and batteries come in operation and voltage starts decreasing, the -48V supplied through brown wire will also decrease which cause the CPU to safely shutdown when the voltage threshold is reached i.e 45V.
Then what extra/ different PSAL Chip is doing there?
Any documentation, data sheet of the module to study?
Thanks.

-Muhammad Shahzad Javed

[tgn]

the psal module switches from -48V to 0V (which is marked as +48V in your case) when the threshold (45V) is reached. also the cpu will shutdown, if the psal wire is deconnected (because of a pull up resistor).

regards...

[bingo]

well in stand alone systems, if the PSAL is not working just jump -48 to the PSAL connector ,, behind the system..