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
