KX-PRW110RUW, KX-PRW120RUW, KX-PRWA10RUW - Panasonic Telephone Service Manual (repair manual). Page 12

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• Bell signal detection
• Clip signal detection
• ON/OFF hook circuit

In the standby mode, Q141 is open to cut the DC loop current and decrease the ring load.
When ring voltage appears at the L1T (A) and L1R (B) leads (when the telephone rings), the AC ring voltage is transferred as
follows;

• B 

→ P101 → C106 → R106 → R107 → IC501 (CID INp) 

• A 

→ C105 → R105 → R108 → IC501 (CID INn)

In the standby mode, Q104 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 handset, Q142 turns on and then Q141 turns on, thus
providing an off-hook condition (DC current flows through the circuit) and the following signal flow makes the loop current.

• B 

→ P101 →D101 → Q141 → Q161 → R163 → D101 → A

• Audio Circuits and DTMF tone signal circuits.

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.

*Refer to Signal Route (P.16).

The voice signal input from the TEL LINE interface goes to 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 IC501, the carrier frequency is changing, and frequency modulated RF signal is generated.In IC501,RF signal is amplified,
and radiated from antenna. Handset detects the voice signal or data signal in the circuit same as the following explanation of
Receiver Block.

The signal of 1900 MHz band (1881.792 MHz ~ 1897.344 MHz) which is input from antenna is input to IC501 as shown in Block
Diagram (Base Unit) (P.8).
In IC501, the signal of 1900 MHz band is downconverted to 864 kHz signal and demodulated, 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.

During pulse dialling the hookswitch (Q141, Q142) 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 Q144.

BBIC and WiFi module are connected with 3group signals as shown in Block Diagram (Base Unit) (P.8).

SPI (Serial Peripheral Interface) Control --- Control the data (except Audio data) between BBIC and Wi-Fi module
Interrupt Control   --- Control the timing of sending/receiving of BBIC and Wi-Fi module
PCM (Pulse Code Modulation) Control --- Control the Audiol data between BBIC and Wi-Fi module.

When turning ON, it start to communicate between BBIC and WiFi module by SPI Control with Interrupt control to set various
data into the register of WiFi module and then it becomes Stand-by status.
WiFi network data, such as MAC address is transferred to Memory of WiFi module from BBIC's one.
For talk with Smartphone via WiFi, audio signal is modified to PCM signal then communicated.