138. Clockwork-Fuze Detecting Set 41 (Zünderhorchgerät 41)

a. General. This equipment is used for the detection of clockwork-fuze mechanisms.

b. Description. Each set, weighing a total of 966 pounds, consists of the following equip-ment:

5

E 150c detector heads, each with 660 feet of cable and folding cable-reel stand.

1

EVB 9 amplifier with two headsets.

1

12 NC 28 battery.

(1)

Detector heads. The E 105c detector head is the same as that used with the mine gallery-detector set 40 (par. 135).

(2)

EVB 9 amplifier. The amplifier EVB 9 differs from the type EVB 6 (par. 135) in the following details:

(a)

The amplifier is in four stages – three screen-grid amplifiers followed by an cut-put triode. All electron tubes are RV 12P 2000. Power is supplied, as in the EVB 6, from a 12-volt battery through a built-in vibrator pack, which has more than normal suppression to eliminate low-frequency interference. A selector switch connects to any desired detector head, and a coupling switch links all heads together in position ALL. In this case a resistance in the grid circuit of the second stage is short-circuited. For using the selector switch for single de-tector heads, the coupling switch must be in the position SINGLE.

(b)

Frequencies under 300 cycles are blocked by a high-pass filter between the first and the second amplification stages. The gain control is in the grid circuit of the second stage.

(c)

Operation begins with all the detector heads connected. When clockwork vibrations are detected, the source of the vibrations is located by using the SINGLE and selector switches to determine the detector head which requires the least gain.

(3)

12 NC 28 battery. This piece of equipment is the same as that described in para-graph 135.