M 1 Unit. The original type of hand-set BIK, designed for use in ground mines, was designated E-BIK for "Einer nadel BIK" (single-needle BIK), and the multiple-needle type for moored mines designated M-BIK for "Mehrer nadel BIK" (Multiple-needle BIK). Later the automatic latitude adjuster was applied to both. They were then called SE-BIK for "Selbst einstell E-BIK" and SM-BIK. The E-BIK was laid in 1939 and was designated M Mk I by the Allies. The SE-BIK was laid in 1940, and was similary designated M Mk II. When the German nomenclature was systemitized, the SE-BIK was designated M 1 by the Germans. This device went through some small improvements known as M Mk III and M Mk II (revised) to the Allies, but retained its original German designation. In 1941 the Germans laid the SM-BIK in the TMA mine. They considered this unit unsuccessful and experimental, and it was withdrawn from service. However, it was designated M 2 (Allied designation M Mk VII). Captured material examined indicates that the Germans conduct-ed considerable experimental work on the movement of ground mines in mud. As a result, they felt that too much battery energy was being expended by excessive pendulum action in the normal M 1 unit. The first attempt to save the battery was by the use of two pendulums; one sensitve and one insensitive. This device was never used operation-ally.

Figure 137 – M 1 Unit Housing

Figure 141 – M 1 Unit for LMA/LMB Mines

Figure 142 – M 1 Unit - Hand Set - Front and Side

Figure 143 – M 1 Unit - Two-Pendulum