Panasonic KX-FP362CX Service Manual page 97

Digital Block Diagram
You also need to check the signal lines listed here [List 1] when the unit fails to boot up the system. Those signal lines should
remain normal. Other signal lines are not directly related to that failure even if they have faults or troubles.
As long as these signals remain normal, once the power is turned on, each IC can repeatedly output 3.3V (H) and 0V (L) (IC503
and IC520 output 5V(H) and 0V(L)). The following shows NG and normal wave patterns.
NG Wave pattern (Refer to NG EXAMPLE)
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KX-FP362CX