KX-TU301EXME - Panasonic Telephone Service Manual (repair manual). Page 9

9

When charging with Charger, the charge current is as follows:
DC+(5.5V) 

→ F1(Charger)→ CHARGE+(Charger) → CHARGE+(Handset) → CN4 → L1 → Q1 → F2 → IC1 → IC2 →

BATTERY+... BATTERY- 

→ L2 → CN4 → CHARGE-(Handset)→ CHARGER-(Charger) → DC-(GND)

When charging without Charger, the charge current is as follows:
DC+(5.5V) 

→ JK1 → D1 → F2 → IC1 → IC2 → BATTERY+...

BATTERY-

→JK1→DC-(GND)

In this way, the BBIC on Handset detects the fact that the battery is charged.
The charge current is controlled by IC2 of Handset.
Refer to Fig.102 in Power Supply Circuit (P.8).

Fig.102

“Battery Low” and “Power Down” are detected by BBIC which check the voltage from battery.
The detected voltage is as follows;

• Battery Low

Battery voltage: V(Batt)   3.5 V ± 50 mV
The BBIC detects this level and "

" starts flashing.

• Power Down

Battery voltage: V(Batt)   3.3 V ± 50 mV
The BBIC detects this level and power down.

• Establish and control the connection with GSM network
• SIM card interface
• Transmitter/Receiver

The voice signal input from MIC is coded and modulated to the GSM RF signal (GSM900 band: 880-915MHz/DCS1800
band:1710-1785MHz) in BBIC(IC1). GSM RF signal is amplified and radiated from antenna.
The GSM RF signal (GSM900 band: 925-960MHz/DCS1800 band: 1805-1880MHz) which is input from antenna is input to BBIC
(IC1) as shown in Block Diagram (Handset).
In IC1, the RF signal is demodulated.The voice data is decoded to analog audio and output through receiver or speaker.

• Keypad Interface
• Color display are supported
• Keypad and display backlight supported
• Speaker driver
• Receiver driver
• Headset driver
• Microphone input
• Charger circuitry for NiMH cells

The hands-free loudspeaker at SP+ and SP- is used to generate the ring alarm.