M 1 (1st Revision) Unit Circuit - Operation (Figure 139).

Arming. Same as original unit except that if S2 does not open properly as the preset sensitivity is applied, the A.L.A. arm momentarily closes S4, completing the circuit through the hold-off coil and S2, opening S2.

Normal Firing and Anti-Countermining. Same as the original M 1.

Figure 139 – M 1 Unit (First Revision) Circuit