Panasonic KX-TG5776S Service Manual page 28

KX-TG5776S/KX-TG5777S/KX-TGA571S
4.8.7. USB Signal
Q291-Base1 detects that USB-cable is connected to the unit, which is recognized by pin 39 of DSP.
Then 3.3 V is made by IC291 under the control of pin 21 of DSP. And a signal is output to inform of the completion of the USB-
cable connection.
The USB-data signals (D+, D-) are input/output at pin 10 and 11 of DSP.
Q291-Base2 detects the condition of the USB-data communication, which is recognized by pin 40 of DSP.
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