Installation guide

Williams Sound
®
Helping People Hear
21
FREQUENCY CHANGE INSTRUCTIONS
Normally, the PPA 250’s factory-set channel (usually 72.9 MHz) requires no change.
However, if another hearing assistance system or authorized radio service is operating on
72.9 MHz in your area, it may prove necessary to use an alternate channel
In this event, the PPA System 250’s operating frequency can easily be changed to an alternate
channel to avoid interference.
See the following sections for instructions on changing frequencies.
TRANSMITTER FREQUENCY CHANGE PROCEDURE:
Set the T4 Transmitter to any of the 10 available channels using the FM Channel/FM Power
Switch. See figure 9.
IMPORTANT: Some cities have other radio services licensed on hearing assistance
channels. Under FCC rules governing hearing assistance, you must yield to
them. A list of cities where other radio services are known to exist is
included with the transmitter. Do not use frequencies that are known to be
used by licensed radio services in your city, either if they are on the list or if
you discover one.
RF CONFIG SWITCH
SWITCH SETTINGS
FREQUENCY
RF OUTPUT POWER
ON
ONON
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON ON
ON
ON
ON
ONON
ON
ON
ONON72.100 MHz
72.300 MHz
72.500 MHz
72.700 MHz
72.900 MHz
74.700 MHz
75.300 MHz
75.500 MHz
75.700 MHz
75.900 MHz
FULL
HALF
QUARTER
OFF
ON
ON
ON
67834521
OFF OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF OFF OFF OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
Figure 9: FM Channel/FM Power Switch Settings
Switches 1-5 toggles control
frequency settings
Switch 6 is not used
Switches 7 and 8 control RF output
power. The factory setting is FULL, and
can be adjusted if conditions warrant.
See Troubleshooting Guide.
Remember: If you change the
transmitter frequency, you must also
change receiver frequencies.
“On” and “Off are labeled on the
body of the DIP switches.