A wiring diagram for a simple annunciator system is shown in Fig. 75. The pushes 1, 2, 3, etc. are located at convenient points in the various rooms, one terminal being connected to the battery wire b and the other to the leading wire l communicating with the annunciator drop corresponding to that room. A battery of three or four Leclanche cells is placed at B, in any convenient location, but should not be set in a dark or inaccessible spot, or be exposed to frost.