Yaesu FT-1000 Operating Manual page 20

(page 9).
(2) GND Terminal Post
(3) ANT Coaxial Jack
(4) RX ANT Phono Jack
This antenna jack is for a separate receive-only
antenna, activated when the switch with the same name
on the front panel is pressed. If the BPF-1 option is not
installed, an antenna connected here can be used by
both the main and sub receivers. If the BPF-1 is in-
stalled, internal switch $1001 on the RF Unit deter-
9)
If your amplifier requires higher current, or has
higher voltage switching requirements, an external
switching device such as the Yaesu FRB-757 Relay
Box must be used, and may be connected here.
(6) +13.5¥ Phono Jack
This output jack provides regulated, separately
fused 13.5 VDC at up to 200 mA, to power an external
device such as a packet tnc. Make sure your device
does not require more current (if it does, use a separate
power source). Attempting to draw more power from
here will blow the internal fuse behind this jack.