Instruction manual
Setup and Installation
025-9209 39
If your radio provides a logic change of 5-0 V
dc
when channel is busy, install JP1 in the A
position and leave the RTU setting for Carrier detect as the factory default setting of low.
If your radio provides a relay contact closure to ground or open collector output, install JP1
in the B position and leave the RTU setting for Carrier detect as the factory default setting of
low.
You may wish to refer to “Channel Busy Detect” (on page 11) which discusses the carrier
detect setting. There is a software controlled LED that will be lit when carrier is detected
(based on what was set during configuration).
PTT
JP3 A = PTT completes the connection between P3 Pin 3 and Pin 4.
B = PTT provides a ground on P3 Pin 3. (Pin 4 not used)
JP4 IN = PTT provides a +5 V
dc
pull-up on P3 Pin 3 when not engaged.
OUT = PTT goes to an open circuit on P3 Pin 3 when not engaged.
Step 3. Transmit and Receive Audio Adjustment
Connect two RTUs to their radios and power supply, and turn power on.
There are two jumpers located on the PCB next to the large square IC. These jumpers are
labeled Test A and Test B. With power on, putting a jumper on Test A and/or Test B will
cause the unit to enable Push to Talk and send the tones listed in Table 20.
Table 20. RTU Audio Adjustment Test Tones
Test A Test B Tone
out out None
out in 1200 Hz
in out 1800 Hz
in in Alternating 1200 and 1800 Hz
In RTU #1, put test A and test B jumpers in place. This will cause the radio to key up and
transmit an alternating 1200 Hz and 1800 Hz tone.
On RTU #1, adjust the TX AUD pot to provide an audio output level that meets the radio
manufacturer’s specification.
Look at TP1 on RTU #2 with an oscilloscope or voltmeter with an AC setting. Use any
ground point, such as the metal enclosure, as a reference. Adjust the RX AUD pot and JP7 on
RTU #2 until TP1 measures 1 V
pp
.
JP7 A = Low 1x gain on Receive Audio
B = High 10x gain on Receive Audio