Read Panasonic KX-NCP1171XJ (serv.man2) Service Manual online
9
KX-NCP1171XJ
• PT current-supply circuit
+15V/+40V is superimposed on the transmit/receive data line (D1, D2), and fed to PT. Supply voltage is +15V for old DPT and
APT, and +40V for new DPT. It will be switched after the connected PT is judged through communications. I/O control is as
follows.
APT, and +40V for new DPT. It will be switched after the connected PT is judged through communications. I/O control is as
follows.
For the protection against such as an overcurrent owing to +15V short in wiring, 300mA constant-current circuit by Q1, Q2, and R25
is used. In case of +40V, 20mA and 80mA constant-current circuits by Q4, U3, R7, and R27 are used.
The following is the flow chart of telephone switching at boot-up.
is used. In case of +40V, 20mA and 80mA constant-current circuits by Q4, U3, R7, and R27 are used.
The following is the flow chart of telephone switching at boot-up.
PT_POW
PT_CUR
H
H
15V
H
L
0V
L
H
40V80mA
L
L
40V20mA
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