Icom IC-251A Instruction Manual page 10

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10.
. MIC CONNECTOR
Connect the supplied microphone or optional microphone to this jack. The |C-SM5 stand-type
Electret microphone can also be used. If you wish to use a microphone other than one of
these, refer to the drawing on page 6.
. SQUELCH CONTROL
Sets the squelch threshold level. To turn OFF the squelch function, rotate this control
completely counterclockwise. To set the threshold level higher, rotate the control clockwise.
The squelch function operates in all modes.
. AF GAIN CONTROL
Controls the audio output level in the receive mode. Clockwise rotation increases audio
output.
. RF GAIN CONTROL
Controls the gain of the RF and IF section in the receive mode. Clockwise rotation gives
maximum gain with no signal present. As the control is rotated counterclockwise, the needle
of the Multi-Function meter rises, and only signals stronger than indicated on the meter will
be heard. This will eliminate noise during the absence of signals.
. MODE SELECT SWITCH
This switch selects the mode of operation for both transmit and receive. The initial letter of
each mode is displayed on the frequency display unit according to the switch setting.
FM-c Frequency modulation, and the Multi-function Meter functions as a discriminator
meter in the receive mode.
FM-s Frequency modulation, and the Multi-function Meter functions as a signal strength
meter in the receive mode.
USB Upper Sideband
LSB Lower Sideband
CW Continuous Wave, for CW operation
VFO/MEMORY SWITCH
Selects an operating VFO from "A" VFO and "B" VFO, and selects the other various
operations.
A>B Instantly sets the frequency of "B" VFO to the same as that of "'"A'' VFO.
MS. Sets the MEMORY SCAN function. Push the MS/MW Button to start scanning the
three programmed frequencies in Memory Channels 1, (2! and 3).
A Selects "A'' VFO for both transmit and receive. Programmed Scan "'A"' is started
by pushing the MS/MW Button while at this setting.
B Selects ""B'' VFO for both transmit and receive. Programmed Scan ''B" is started
by pushing the MS/MW Button while at this setting.
RA-TB _ Selects '""A'' VFO for receive and "B'' VFO for transmit.
RB-TA Selects ""B" VFO for receive and ""A'' VFO for transmit.
1, [2],{3] Selects the three Memory Channels. [2/ and [3] are also used for Programmed Scan
operation. For details of this operation, refer to MEMORY CHANNEL OPE-
RATION on page 20.