Icom IC-12GAT Instruction Manual page 27

. RELATED FUNCTIONS 8.
8-10 LOCK The LOCK function disables all switches except
FUNCTION [H/L], [MONI], [PTT] and [LIGHT], preventing
accidental frequency changes, etc.
1) While pushing [FUNCTION], push [H/L] to
lock all switches.
e "L" appears on the FUNCTION DISPLAY.
2) Repeat step 1 to unlock the switches.
When the LOCK function is ON, these switches
remain unlocked:
[PTT]
[LIGHT]