Specifications

2–14

FM500 User's Manual

Pin Number Function

1 Ground

2 (no connection)

3 Composite Out (sample of stereo generator output)

4 FSK In (Normally high; pull low to shift carrier

frequency approximately 7.5 kHz. Connect to open

collector or relay contacts of user-supplied FSK keyer.)

5 /Auto Carrier Off (Pull low to enable automatic turnoff

of carrier with program failure.)

6 Meter Battery (unregulated DC volts; 5 volts = 50 VDC)

7 Meter RF Watts (1 volt = 100 watts)

8 Meter PA Volts (5 volts = 50 VDC)

9 /Ext. Enable (Pull low to disable internal stereo

generator and enable External Composite Input.)

10 a) 38 kHz Out (From stereo generator for power supply

synchronization.)

b) For transmitters equipped with tuner option, this pin

becomes the right audio output for an 8–ohm monitor

speaker. 38kHZ Out is disabled.

11 ALC

12 /Carrier Off (pull low to turn carrier off.)

13 Fault Summary (line goes high if any fault light is

activated.)

14 Meter PA Temperature (5 volts = 100 degrees C.)

15 Meter PA Current (1 volt = 10 amperes DC.)

Illustration 2–15 Remote I/O Connector (outside view)

Table 2–3 Remote I/O Connections