19519P-54 (01-20) 3 of 5
Note: The U3816 Radio Receive Level Adjustments cannot increase the Radio Receive Level to a
level that is higher than set by the radio. If the Receive Level of a Radio is too low, adjust the Level at
the Radio until sufficient level is achieved.
6. To transmit over a mobile radio, depress and hold the radio PTT button corresponding to that radio, and
speak into the microphone in a clear, normal level voice. Release the PTT button when finished.
Note: Radio speakers, mounted near the headset, may produce acoustic feedback, causing a squeal
when transmitting. If this occurs, reposition the speakers to eliminate the feedback.
a) If Part Number 40071G-04 Footswitch is installed,the footswitch may be used to key the
corresponding radio,instead of the PTT button on the U3816. To transmit over a mobile radio using
the footswitch, depress and hold the footswitch, and speak into the microphone in a clear, normal
level voice. Release the footswitch when finished.
b) If Model C3023 Belt Station is installed, the PTT Switch on the C3023 may be used to key the
corresponding radio instead of the PTT button on the U3816. To transmit over a mobile radio using
the C3023 Belt Station, depress and hold the remote PTT button on the C3023, and speak into the
microphone in a clear, normal level voice. Release the PTT button when finished.
CONSIDERATIONS
1. If both mobile radios are keyed simultaneously, there is a possibility that the radios could overload each other.
This may cause damage to the radios. The closer the frequencies of the radios, and the closer their
corresponding antennas, the greater the likelihood of this occurrence. A similar phenomenon may occur if one
radio is transmitting while the other is receiving. Consult the radio manufacturers’ for their recommendation
concerning antenna spacing and frequency spread.
Whenever possible, transmit on only one radio at a time.
2. In some vehicles, with excessive alternator whine, it may be necessary to insert a Power Line Filter between the
power connection and the U3800 Master Control. Power Line Filters are available through most electronics
distributors.
3. If stand-alone operation is desired, the U3816 may be powered directly from switched battery power (+13.8
VDC) from the vehicle. For this mode of operation, the vehicle switched battery (+13.8 VDC and GRD) should be
connected to the V REG pin and GND pins of the appropriate mating MS connector at one of the system ports
(e.g., modified C38-xx jumper cable, on white [V Reg] and black [GND] conductors). An in-line fuse-holder kit
(p/n 09487P-09), along with a 1A fast-acting fuse (p/n 09486P-09) are recommended for this application.
In addition, the jumpers JP1 (corresponding to Radio 1) and JP2 (Radio 2) on the printed circuit board must be
positioned for Radio-Isolated mode, per 2e. above (see Figure 1 for jumper locations on the printed circuit
board.)
It is important to note that in stand-alone operation, there will be no side-tone in the headset. Receive audio will
come from the radio only.
