Operating instructions
Page 10    RF Technology R350/R500 
3  RECEIVER I/O CONNECTIONS  3.1 25 Pin Connector 
3   Receiver I/O Connections 
3.1   25 Pin Connector 
The D-shell 25 pin connector is the main interface to the receiver. The pin 
connections are described in table 3.  
Function  Signal  Pins  Specification 
DC Power  +12 Vdc 
 0 Vdc 
1, 14 
13, 25 
+11.4 to 16 Vdc 
 Ground 
Channel Select  1 
2 
4 
8 
10 
20 
40 
80 
21 
9 
22 
10 
23 
11 
24 
12 
BCD Coded 
0 = Open Circuit 
or 0 Vdc 
1 = +5 to +16 Vdc 
RS232 Data  In 
Out 
15 
2 
Test and Programming use 9600, 
8 data 2 stop bits 
600Ω Line 
In 
Out 
20 
6 
Transformer Isolated Balanced 
0dBm Output 
150Ω / Hybrid 
  7 
19 
Discriminator    18  AC coupled, unsquelched 
Direct Audio Output    17  Direct AC Coupled Audio 
Audio Ground    5  Direct Audio Ground 
Sub-Audible Audio 
Out 
  4  Unsquelched, 1-250 Hz 
Carrier Operated Sw 
Carrier Operated Sw 
COS [+] 
COS [-] 
3 
16 
Opto-coupled Transistor Switch 
(10mA 30V max) 
External Squelch  Input  8  <1 Vdc to Squelch 
>2 Vdc or open ckt to  
unsquelch 
Table 3: Pin connections and explanations for the main, 25-pin,  
 D-shell Connector 










