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a combination of components selected from R85, R86, C93, C37 and R1. The combination
depends upon the CLIP requirements of the specific country - often there is no requirements for
the CLIP_STATE impedance.
T10 disables the CLIP signal during the off-hook condition.
6.2.5. HOOKSWITCH (SEE Fig. 19)
T8 is the hookswitch, driven by T9. When the phone is "off-hook", the HOOK control signal from
the BBIC will be a high logic level (+2.7V), and both transistors will be on, thus T8 will "loop" the
line. The zenner diode D10 protects transistors T11 to T13 against transient line voltages.
6.2.6. AUDIO CIRCUITS (SEE Fig. 19)
The loop current (typically 40mA) passes through T13, R57 and R56. R54 and R55 provide dc
biasing for the base of T13.
The line output signal from the BBIC RXAF is DC decoupled by C47 and amplified by T13. The
emitter load (R57, R58 and C46) is complex in order to achieve the right frequency response
with the complex line impedance.
The line input signal TXAF is taken from the junction of R41 and R49. Phase cancellation is
provided at this point by R70 so that only the incoming line audio should be passed to the BBIC
on TXAF.
Circuit Diagram
6.2.7. POWER SUPPLIES (SEE Fig. 20)
The AC adaptor for the KX-TCD715 provides unregulated DC through J2 for the handset charge
terminal, 6V regulator (IC1) the 3.8V regulator (IC7) and the Relay coil (RL1) where fitted.
The 3.8V supply from IC7 is used for the RF module, and is further reduced by IC11 to 2.7V for
the BBIC supply.
The 6V supply from IC1 is used for SP-Phone AMP. (IC14).
R17, 18 and 28 provide short circuit/over current protection at the handset charge terminal.
R109, D6, T1, R110, R111, R112 and D11 are charge detection circuit, in order to detect whether
put Handset on cradle or not.
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