The segmented readout displays (fig. 5-76) are twoand five-digit numerical readouts located on EP2. The two-digit displays indicate round quantities loaded in the loader drum and lower hoist. The five-digit displays are used along with the built-in-test features of the control system (refer to fig. 5-19) for troubleshooting.

Figure 5-76.-Segmented readout displays,

Wire-Wrap Backplane

The wire-wrap backplane (fig. 5-77) is a wiring board inside EP2 that interfaces circuit cards PC1 through PC140. The backplane contains circuit card receptacle connectors, backplane connectors, pins, wires, and a board. Wires are wrapped around pins providing electrical connection between circuit cards and between the circuit cards and the backplane connectors located at the bottom of the assembly. The backplane connectors provide external interfacing for all control signals leaving or entering the backplane as well as the +5 VDC and +25 VDC power supplies

Figure 5-77.-Wire-wrap backplane.

needed by the circuit cards. A large cover which mounts on the backplane protects the wire-wrap pins and wires.

SOLID-STATE CONTROL CIRCUIT OPERATION

LEARNING OBJECTIVE: Recall general information concerning operation of a Mk 13 Mod 4 GMLS solid-state control circuit.

We will now describe the operation of an actual solid-state control circuit. Our example comes from the Mk 13 Mod 4 GMLS and pertains to the retractable rail of the launcher.

The normal position of the retractable rail is to be extended, ready for launcher loading. When the GMLS is in auto-load mode, the rail retracts automatically during two operations: (1) missile firing and (2) dud jettisoning. When the GMLS is in step control, the rail can be retracted in two modes: (1) step-load and (2) step-exercise. Usually the rail is not retracted during step-load operations. However, in conjunction with a step-jettison operation, a loaded rail can be retracted if required. Bear in mind, this operation is not a normal circumstance, but it is available. In step-exercise, the rail must be empty/not loaded during a retract cycle. Depressing the correct push button on the EP2 console initiates the desired operation.

Figure 5-78 shows the schematic used to retract the launcher rail electrical y. Take a moment to review the drawing. Some of the items you should notice include the following:

1. A variety of AND, OR, and OR-AND logic gates. Refer to table 5-2 as we go through these gates. There are no polarity indicators (flags) used.

2. A latching relay and a solenoid driver circuit are used.

3. A +5-volt dc logic supply controls the +26-volt dc (+25-volt dc backup) relay, solenoid, and miscellaneous power supplies.