Panasonic KX-TEA308NE, Service Manual

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1) Conference switch
Normally, pin 6 of the analog switch IC2 is low level, but during conferences, this pin becomes high level. Because, during
conferences, it should compensate the return loss by connecting the balance network BN2 and the balance network BN3 in
parallel.
2) Mute switch
The mute switch consists of pin 13, 1 and 2 of the analog switch(IC2). This switch has the following functions.
a) When a dial signal (DP) is sent to the COL, signals from the extensions are blocked.
b) When the hold on music is sent to the COL, signals from the extensions are blocked.
c) When the COL interface circuit is in the idle state, oscillation of COL bidirectional amplifier is inhibited. When pin 13 of IC2
changes to low level, the interval between pins 1 and 2 of the analog switch turns off, and signals are blocked.
3) Shunt switch
The shunt switch consists of pin 12, 10 and 11 of analog switch IC2.It is used to prevent the pulse dialing signal which is
transmitted to the extensions. When pin 12 of IC2 changes to high from low, the analog switch becomes ON (the interval
between pin 10 and 11), and GAIN of the COL cross point operational amplifier becomes zero.
Shunt SW Mute SW Conference SW
pin no. of analog switch 12 13 6
No connection (idle) H (on) L (off) L (off)
Two party call L (off) H (on) L (off)
Conference L (off) H (on) H (on)
Hold on music transmission H (on) H (on) L (off)
Condition of COL interface amplifier circuit and analog switches.
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KX-TEA308NE