B61 Nuclear Bomb Preflight Controller
The two-digit switches labeled TA and TB specify two "safe separation" times in seconds. This defines the time that must elapse after the bomb is released from the aircraft before detonation can occur.
The switch labeled delivery specifies one of two options for the fall of the bomb: FF (freefall) or RE (parachute retarded). [..] Some models of the B61 have an additional delivery option of "laydown". This is like parachute-retarded groundburst except that detonation is delayed for some period of time after contact.
The delay switch controls the delay between separation and deployment of the parachute (in the case of retarded fall). The options we have are G (0.3 s deployment delay), H (0.6s delay), and J (1.6s delay). In the case of a laydown delivery, this switch also controls the delayed detonation time.
The function of the switch labeled option is redacted from my copy of the B61-7,8 report. A reasonable guess is that the option switch controls the yield; most B61 versions have multiple selectable nuclear yields.
The MC4142 "strike enable plug" (figure 12) is just that: this plug must be inserted to complete critical circuits in the arming and firing mechanisms.
The three numeric switches at the bottom, together with the swich right above them and the T-handle are used to initiate "command disable". This option will perform a "non-violent" function within the nuclear explosive component that disables the device from being able to detonate.
Then an interlock on the above four-position switch is released and it can be turned from "N" (normal or nuclear, I guess) to "DI" (disable). [..] To initiate the command disable function, the appropriate code is set in the three code wheels.