IBM ThinkPad R40 2681 Hardware Maintenance Manual page 75

Antenna cables 4a and 4b are for the wireless LAN
feature.
Note: When unplugging the antenna jack, do not pull the
cable; it might snap. Unplug the jack by pulling a
tab with your fingers.
When installing: Plug the gray antenna cable with the tab
(continued)
4b
marked "MAIN" ( 4a ) into jack J1, and
the black antenna cable with the tab
marked "AUX" ( 4b ) into jack J2.
Removing and replacing a FRU
4a
ThinkPad R40
71