Panasonic KX-FLB852CX Service Manual page 219

In order to stop the motor rotation, following 2 signals are supplied from IC604.
1. SS signal
Output pin: Pin 120/Output Signal: "L"
Consequently "Start/Stop" signal becomes "H".
2. Break signal
Output pin: Pin 122/Output Signal: "H"
Motor stops rapidly by changing the "Break" signal from "L" to "H".
Timing Chart of Start operation
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KX-FLB852CX / KX-FLB852CXS