Panasonic KX-TG9385BXT Service Manual page 11

4.3.3. Telephone Line Interface
Note:
[ ]: Line 2
<Function>
• Bell signal detection
• Clip signal detection
• ON/OFF hook circuit
Bell & Clip (: Calling Line Identification Presentation: Caller ID) signal detection:
In the standby mode, Q101 [Q201] is open to cut the DC loop current and decrease the ring load.
When ring voltage appears at the L1T (A) [L2T (C)] and L1R (B) [L2R (D)] leads (when the telephone rings), the AC ring voltage
is transferred as follows;
ON/OFF hook circuit:
In the standby mode, Q101 [Q201] is open, and connected as to cut the DC loop current and to cut the voice signal. The unit is
consequently in an on-hook condition.
When IC501 detects a ring signal or press the TALK Key onto the cordless handset, Q103 [Q203] turns on and then Q101,
PC102, Q102 [Q201, PC202] turns on, thus providing an off-hook condition (DC current flows through the circuit) and the
following signal flow makes the loop current.
A [C] → D101 [D201] → Q101 [Q201] → Q131 [Q231] → R124 [R224] → R125 [R225] → Q102 [-] → D101 [D201] → B [D]
4.3.4. Transmit/Receive the signal
Base unit and handset mainly consist of RF Module and DECT BBIC.
Base unit and handset transmit/receive voice signal and data signal through the antenna on carrier frequency.
Signal Path:
*Refer to voice data of Signal Route (P.15).
Transmitter and receiver block of DECT RF describes as below.
4.3.4.1. Transmitter Block of DECT RF (For receiving of voice signal)
The voice signal input from the TEL LINE interface goes to RF Module (IC801) through DECT BBIC (IC501) as shown in Block
Diagram (Base Unit) (P.8)
The voice signal passes through the analog part of IC501 where it is amplified and converted to a digital audio stream signal.
The burst switch controller processes this stream performing encryption and scrambling, adding the various other fields to
produce the GAP (Generic Access Profile) standard DECT frame, assigning to a time slot and channel etc.
In IC801, the carrier frequency is changing, and frequency modulated RF signal is generated and amplified, and radiated from
antenna. cordless handset detects the voice signal or data signal in the circuit same as the following explanation of Receiver
Block.
4.3.4.2. Receiver Block of DECT RF (For transmitting of voice signal)
The signal of 1900 MHz band (1920 MHz ~ 1930 MHz) which is input from antenna is input to IC801 as shown in Block
Diagram (Base Unit) (P.8).
In IC801, the signal of 1900 MHz band is downconverted to 864 kHz signal and demodulated, and goes to IC501 as GAP
(Generic Access Profile) standard DECT frames. It passes through the decoding section burst switch controller where it
separates out the frame information and performs de-encryption and de-scrambling as required. It then goes to the DSP section
where it is turned back into analog audio. This is amplified by the analog front end, and goes to the TEL LINE Interface.
4.3.5. Pulse Dialling
During pulse dialling the hookswitch (Q101, Q102, Q103, PC102/Q201, Q203, PC202) is used to generate the pulses using the
HOOK control signal, which is set high during pulses. To force the line impedance low during the "pause" intervals between dial
pulses, the PULSE_DIAL signal turns on (Q101, Q102/Q201).
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KX-TG9385BXT/KX-TGA939BXT