Mode S
At the risk of winding Walter up ......... Did they even have Mode S? I'm pretty sure I didn't on my state of the art aluminum pursuit ship at the time - we only fitted it for overseas operations.
Or am I confusing it with Mode IV - too much claret methinks!
Anyway if I wanted to set an emergency code I'd rotate the switch to emergency and not faff about changing individual dial numbers - thats how some clever bu&&er designed it to be used.