Specifications

Technical Manual Installation and Operation
RELM/ BK RADIO
31
8. Appendices
8.1 SMX920 Interface Connections
The user connections to the SMX920 are all made via the Front and rear panel where
the following connectors are located.
No Conn Type Function Description
CN6 N TYPE Simplex relay out or
N type RX input
Location for internal simplex relay. The
antenna for RX / TX connects to this
point. Alternatively a N-Type
connector can be used for the input to
the receiver for full duplex operation
CN7 N TYPE TX output The RF power output from the
transmitter for full duplex operation.
SKL RJ45 Microphone Socket
and RS232
Communication
The socket provides a connection for a
microphone. Also provides RS 232
Communication between radio and PC
See Table 8-2
Table 8-1 SMX920 Interface Connectors
Pin No Function Comment
1 Low level muted RX VF Filtered and De-emphasis.
2 +8V DC Current limited.
3 Microphone PTT Pulled to +5V via 10k resistor. Connect
to ground for PTT.
4 Microphone VF 600 ohms Z, gain and compression
functions are software controlled.
5 EARTH common Pin 5 DB9M (PC RS-232).
6 Hook / Monitor switch For quiet base use. Connect to ground
for quiet base operation.
7 RS-232 RxD Pin 2 DB9M (PC RS-232).
8 RS-232 TxD Pin 3 DB9M (PC RS-232).
Table 8-2 SMX920 Accessory Socket Pinout
The RJ45 pins are numbered as shown in Figure 3-4 below.
Figure 8-1 RJ45 socket viewed from front of SMX920
1 .................. 8