LG GDK-20W User Manual

GDK-20W DIGITAL WIRELESS KEY TELEPHONE SYSTEM     
 

 

 

 
The system can be equipped with external batteries for proper operation when local AC power fails. The Back-Up 
batteries are connected to the connector(CN3) of the MFB. 
 
The External batteries must provide 24 Volts DC. This is generally accomplished by connecting two 12 volts batteries in a 
series arrangement. Battery operation is controlled by the MFB. The MFB will provide charging current(maximum 0.5 
amp) to the batteries during normal AC power operation. The MFB will automatically stop the battery operation when AC 
power re-applied or low battery voltage detected. 
The system operating time by external batteries is depend on several elements as follows, battery charge state, condition 
of the batteries, capacity of the batteries, and the system configuration(number of station ports).   
The MFB has one industry standard 9 pin RS-232C connector. The RS-232C ports are connected by 9-pin connectors as 
shown Figure 3.5.2. Note that the communication settings are 9600bps(Max 38400bps), 8 bit data, no parity bit and 1 
stop bit. 
The RS-232C port only provides three(3) control signals such as TXD, RXD and ground.   
It is recommended that the RS-232C serial cable whose length is below 10 meters is used. 
 
Batteries are connected to the connector(CN3) of the MFB, as shown in Figure 3.5.1. 
 

    -    It is recommended to use a fuse(5A @250V) between battery and system.   
    -    Recommended battery capacity is 24V/10AH MF battery. The system will operate more than 5 hours with 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 

 
 
 

Figure 3.5.1 Battery Back-Up Wiring 

 
 
 
 
 
 
 
 

2(TX) 

3(RX) 

 

5(GND) 

MFB 

RS-232C 

Connector 

(9pin) 

2(RX) 

3(TX) 

 

5(GND) 

Terminal 

RS-232C 

Connector 

(9pin) 

2(TX) 

3(RX) 

 

5(GND) 

MFB 

RS-232C 

Connector 

(9pin) 

3(RX) 

2(TX) 

 

7(GND) 

Terminal 

RS-232C 

Connector 

(25pin)