Uniden PRO 640XL - Manual (Page 7)

Operatinq Procedure
TO RECEIVE
J, Be sure that the power source, antenna and microphone are properly
connected.
2. Turn the unit on by rotating the Volume control clockwise.
3. Set the channel selector switch to the desired channel.
4. Set the Volume control to a comfortable listening level,
5. Listen to the background noise from the speaker. Turn the Squelch control
clockwise until the noise disappears (no signal should be present). Leave the con­
trol at this setting. The squelch is now properly set. The receiver will remain quiet
until a signal is actually received. Do not advance the control too far, or some
weaker signals will not be heard.
6. If the transmission you are hearing has annoying high frequency distortion try
activating the Hi Cut feature.
TO TRANSMIT
1, Be sure the operator has read artd understands DOT AC rules and regulations prior to operating
the transmitter.
2, Select the desired channel for transmission.
3, If the channel isclear, depress the push-to-t^k switch on the side of the microphone and speak
CAUTION; The transceiver Voltage Standing Wave Ratio (V,S.W,R.) measure­
ment must be performed prior to the use of the transmitter. A “V.S.W.R." ratio in
excess of 2:1 may damage the transmitter. Please check your SWR reading fre­
quently by pressing the SWR key.
PREVENTIVE MAINTENANCE
At six to twelve month intervals, the following system checks should be made;
1. Check the Standing Wave Ratio (V.S.W.R.)
2. Inspect all electrical connections
3. Inspect antenna coaxial cable for wear
4. Inspect all screws and other mounting hardware