60 MTM800 Enhanced Mobile Terminal Installation Manual INSTALLATION
11 RX_AUDIO This is the received RX signal. Output impedance approximate 600 Ohms; 
unsymmetrical; 
Output level = 775mV
RMS
12 AUDIO_PA_ENABLE  This is a digital input. High level or pin enables the audio PA. Low level disables the 
audio PA. 
13 SWB + This voltage is available when the radio is switched on.  
The max. current is 1.0A w/o GPS board and 0.8A with GPS board mounted.
14 HOOK This is a high active digital input.  
Low = On hook; High = Off hook
15* SCI_DTR Data Terminal Ready, used for clock input for high speed flashing.  
Reserved for Service Aids.
16 SPEAKER + Positive output of radio's audio PA (see Pin 1).
17* SCI_CTS Radio OUTPUT: Clear To Send.
Reserved for Service Aids
18* SCI_RTS Radio INPUT: Request To Send.
Reserved for Service Aids
19* SCI_RXD Radio OUTPUT: Receive Data.
Reserved for Service Aids
20* SCI_TXD  Radio INPUT: Transmit Data.
Reserved for Service Aids
The 4-wire 3 Volts SCI interface on the accessory 
connector (pins 17 -20) can only be used for flashing of 
radio firmware and programming software features. It can 
NOT be used for communication during normal radio 
operation.
PIN 10: If the ignition line is not used, it needs to be 
grounded for example connected to pin 7 or 8. 
Interference can cause radio to hang.
Table 10  20-Pin Accessory Connector
Pin Function Description