a. Description. The multiple ignition set 44 is an auxilary device to the obstacle detector set 42 (par. 136). Combination of these two sets makes it possible to detonate individu-ally, at required time intervals, five separate mine circuit, all connected to any one de-tecting circuit. Each of the mine circuit may contain resistance up to 30 ohms. The two-core cable for the detecing circuit may be up to 3,300 feet long. The main components of the set are one switch case MZS (fig. 189) (Schaltkasten, MZS); one selector set ZV 1; and six resistance distributors MZV (Verteiler, MZV), three of which are spares.

Figure 189. Switch case MZS mounted on selectro set ZV 1.

(1)

Switch case. Located on the front plate of the switch case is a nine-pole switch (Neunfach-Umschalter) and nine corresponding terminals, one large and eight small, with provisions for connecting eight pairs of electric firing heads. Two additional terminals connect the switch case with the ignitions cable of the selector set ZV 1 on which the case is mounted. A two-core cable is provided for connecting to a blasting machine, which is the source of current. The blasting machine, either 37 or 39 (Glühzündapparat 37 or 39), is used.

(2)

Resistance distributors. Each resistance distributor (fig. 192) consists of four 50-ohm resistances in series with five branch leads. The distributor is housed in a short length of steel tubing which is closed with a waterproof seal.

(3)

Packing. The switch case is stored in the cable compartment of the selector set (fig. 190). The selector set plug and cable are placed in front of the set and fixed in a bracket specially provided, as shown in figure 190.

Figure 190. Switch case MZS packed into compartment of selector set ZV 1.

(4)

Electrical wiring.

(a)

Switch case. The wiring diagram for the switch case is shown in figure 204. The nine-ploe switch allows the connection of eight pairs of firing heads (each pair connected in series) into the circuit. Position 9 (through pole No. 9) is not equipped for insertion of firing heads but is connected to a safety device con-sisting of an anti-spark condenser of 1 microfarad and a discharge resistance of 10,000 ohms connected in parallel.

Figure 191. Wiring diagram of switch case.

(b)

Resistance distributor. Figure 192 shows the wiring of the resistance distributor with the five leads branching to the mine circuits, so that the resistance for successive circuit is increased by 50-ohm increments.

(c)

Entire set. Figure 193 shows the electrical layout for the entire multiple ignition set 44 in use in an acoustically controlled mine field. The switch case is con-nected between the blasting machine and the selector set. One resistance dis-tributor is connected to the M1 plug of each acoustic sentry which is required to control more than one mine circuit. The leads to these mine circuit are all joined to the return lead into plug M2. In all other details, the connections are the same as for standard acoustic obstacles as presribed in paragraph 136.

Figure 193. Wiring diagram of multiple ignition set 44 used in conjunction with detecting devices.

b. Installing.

(1)

The switch case MZS is removed from its shipping position and fixed onto the top plate of the selector set ZV 1 where it is held by a spring-grip arrangement (fig. 189). The connecting cable of the selector set is connected to the two bottom left-hand terminals on the switch case is connected to the blasting machine.

(2)

The wire ends of the firing heads from 16 electric blasting caps are then wound to-gether so as to form eight separate pairs of firing heads. Within each pair, the firing heads are connected in series. The resistance in the firing heads must be the same as those in the electric blasting caps used in the mine circuits. Where possible the electric blasting caps should all be taken from the same shipment, since differences of resistance may cause mis-fires or simultaneous firing of more than one mine cir-cuit.

(3)

The 16 firing heads are placed in their sockets on the top of the switch case and are fixed by means of the slide provided.

(4)

An electric blasting cap is inserted immediately behind the resistance distributor in each mine circuit so that the circuit is broken even if the mines should not fire; in this way, subsequent circuit can still be detonated in case of a misfire in one.

c. Functioning. As shown in figure 194, the resistance distributor connects all the mines circuits in parallel, while giving each a different resistance. The current coming from the blasting machine will take the path where the least resistance is offered and so set off the mines in that particular circuit. At the same time, the firing heads inserted in the same circuit in the switch case are fuzed, thus cutting off the current to the mine cir-cuits and preventing further mine circuit from being fired until the switch is turned to the next position. This brings another pair of firing heads into the circuit.

Figure 194. Functioning of multiple ignition set 44.