Icom IC-251A Instruction Manual page 8

HEADPHONES
Any good headphone set, including stereo type, that has 416 ohms impedance can be used.
With the plug inserted halfway into the PHONES jack, both the headphones and speaker will
operate. This is convenient when others wish to listen in on the station, or you wish to record
contacts using a tape recorder connected to the headphones jack. With a stereo headphone set
inserted this way, however, the headphones will lose the sound on one side. With the plug inserted
completely, only the headphones work.
MICROPHONE
A high quality dynamic microphone with built-in preamplifier is supplied with your transceiver.
Merely plug it into the proper receptacle on the front panel. Should you wish to use a different
microphone, make certain it has a proper preamplifier. Particular care should be excercised in
wiring also, as the internal electrics switching system is dependent upon it. See the schematic for
the proper hook up. |
TR: 2S0661
(cord side
view)
CW KEY
When operating CW, connect the Key to the Key Jack with the plug supplied. The connection of
the plug is shown below.
If the terminals have polarity, be sure to make the correct connection. Note that the keyed
voltage when switching with semiconductors or relays with resistors in the circuit, should be
adjusted to be below 0.4 Volts!
Key Wiring Diagram
GROUND
In order to prevent electrical shocks, TV1, BCI and other problems, be sure to connect a heavy wire
ground, as short as possible, from a good earth point to the ground terminal on the rear panel.