Yaesu FT-991A Operating Manual page 30

Rear Panel
USB Jack
Connect a computer with a commercially available
USB cable to control the transceiver remotely from
the computer using the CAT command.
Inputting/Outputting audio signals and transmission
control can also be done from the computer.
Note:
To control the transceiver remotely from the

computer, a USB driver is required. For details
on the USB driver, visit the Yaesu website.
When using a USB cable connected to a com-

puter, the transceiver may change to the transmit
mode when the computer is started.
EXT SPKR Jack
This is the monaural jack to connect an external
speaker ( 4 Ω to 8 Ω ) .
Connecting an external speaker to this jack will de-
activate the internal speaker.
SIGNAL GND
REM/ALC Jack
Connect the optional remote control keypad "FH-2".
When a device such as a linear amplifier is connect-
ed, this is an external ALC current input jack.
TX REQ
EXT ALC
NC
REMOTE
ANT Jack ( HF/50MHz )
This is the M-type coaxial connector to connect HF
band and 50 MHz band antennas ( 50 ohms ) .
Cooling fan
Page 28
GND
GND
F T-991 Operating Manual