Fig. 318. Line Lamp Mounting
[View full size illustration.]

In the types made by some manufacturers the only difference between the pilot lamp and the line lamp is in the size of the lens in front of it, the jack and the lamp itself being the same for each, while others use a larger lamp for the pilot. In Fig. 319 are shown two individual lamp jacks, the one at the top being for supervisory lamps and the one at the bottom being provided with a large lens for serving as a pilot lamp.

Fig. 319. Individual Lamp Jacks
[View full size illustration.]

Mechanical Signals. As has been stated the so-called mechanical signals are sometimes used in small common-battery switchboards instead of lamps. Where this is done the coil of the signal, if it is a line signal, is substituted in the line circuit in place of the relay coil. If the signals are used in connection with cord circuits for supervisory signals, their coils are put in the circuit in place of the supervisory relay coils. (These signals are referred to in Chapter III in connection with Fig. 23.) They are so arranged that the attraction of the armature lifts a target on the end of a lever, and this causes a display of color or form. The release of the armature allows this target to drop back, thus obliterating the display. Such signals, often called visual signals and electromagnet signals, should be distinguished from the drops considered in connection with magneto switchboards in which the attraction of the armature causes the display of the signal by the falling of a drop, the signal remaining displayed until restored by some other means, the restoration depending in no wise on when the armature is released.

Western Electric. The mechanical signal of the Western Electric Company, shown in Fig. 320, has a target similar to that shown in Fig. 254 but without a latch. It is turned to show a different color by the attraction of the armature and allowed to resume its normal position when the armature is released.

Fig. 320. Mechanical Signal
[View full size illustration.]