moderate cost, reflectors can be resilvered or replated with chromium. Typically, a lamp in service for a
year will require resilvering.
b. Sighting Device. Signal lamps have a front sight on the reflector, in back of the lens frame and a
notched rear sight fastened to a bracket on the rear of the reflector. The rear sight is adjustable both
horizontally and vertically by means of knurled thumbscrews.
c. Focusing Device. The focusing device is a small knurled thumbscrew about 1/2 inch to the right
of the rear of the bulb socket. This screw passes through a collar that encircles the bulb socket. Turning
this screw in changes the position of the bulb in relation to the reflector.
d. Collar Wear. When a lamp is old, it frequently will not focus well because of collar wear.
Repair the lamp by placing a nut or ring underneath the collar to make it longer. A lamp should be torn
down and this focusing device examined to get a proper understanding of its operation.
e. Battery Connections. When the lamp is properly pointed and focused, the brilliancy of the light
is dependant on the following three factors: the number of dry cells used, the method of connecting
them, and the kind of bulb used.
(1) Figure 2-11 shows several cells connected in a series. The carbon pole of one cell is
connected to the zinc pole of the next. When connected, each added cell increases the voltage. The total
voltage is the sum of the voltages for the individual cells. There is a proper voltage for each lamp bulb.
If the voltage is too low, a dim light will result; if the voltage is too high, the bulb will burn out. The
total amperage is the ampere output of one cell. In a series circuit, the amperage does not increase with
additional cells.
Figure 2-11. Cells Connected in a Series
(2) Figure 2-12, page 2-40, shows cells connected in parallel, with all carbon poles and zinc
poles joined together. This method increases the amperage of the circuit, but the voltage is the same as
that of a single cell. In this case, the six batteries act as one battery, with the same voltage as the
individual cell but with amperage six times larger, thereby increasing the number of hours the lamp
stays lit.
2-39
EN0593
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