Icom IC-551D Instruction Manual page 10

10.
. POWER SWITCH
The POWER Switch is a push-lock we switch which controls the input of either AC or DC
. power supplies, whichever is used. When the switch is pushed IN and locked, power is supplied
to the set. When the switch is pushed again and released, power is cut to all circuits except -
the CPU, if the MEMORY power supply is connected to the MEMORY POWER terminal on
the rear panel.
. PHONES JACK
Accepts a standard 1/4-inch headphone plug for a 4 —16 ohm „авварлюпе set. Stereo head-
phones can be used without modification.
. MIC CONNECTOR
Connect the supplied microphone or optional microphone to this jack. The IC-SM2 stand-type
Electret microphone or the IC-HM5 noise cancelling microphone can also be used. If you
wish to use a microphone other than one of these, refer to the drawing on page 6. Micro- .
phone impedance must be 500 — 600 ohms.
. SQUELCH CONTROL
Sets the squelch threshold level. То turn OFF the squelch function, rotate this control
completely counterclockwise. To set the threshold level higher, rotate the control clockwise.
. 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 section in the receive mode. Clockwise rotation gives the
maximum gain.
. 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 іп the receive mode.
USB Upper Sideband
LSB Lower Sideband
CW Continuous Wave, for CW operation
AM Amplitude Modulation, the BFO also functions in this mode.
PASS BAND TUNING (P.B. TUNE) CONTROL
This control allows continuous setting of the pass band selectivity, moving the edge of the -
filter up to approximately 1KHz/—6dB from either the upper or lower side in all modes
except the FM mode. This not only improves selectivity, but also can improve the audio
quality. Тһе normal position is in the center (12 o'clock) position and is 2.4KHz wide.