Wiring up an Annunciator.
A diagram of the connections for an annunciator with a separate bell is given in [Fig. 57]. Where the bell is contained in the case a terminal will be generally found for connection.
Fig. 57
The figure shows a wire running from the battery to one side of each push button. This is the common return, or battery wire, and saves installing two wires from each push. It should be larger, however, than the rest of the wires, generally about No. 16 B. & S.
All the wires for an annunciator should be run before connecting up. There are different methods of sorting out the wires at the annunciator. One way is to connect the wires (except of course common or battery return wires) to the drops in any order. Then an assistant travels from push to push and presses each button, noting the room numbers and the order in which they were visited.
As each drop falls, its number and order is noted.
Comparing this with the list made by the assistant will show the correct changes to make.
Fig. 58
For instance, suppose pushes 1, 2, 3, 4, 5 and 6 were pressed in that order, and drops 3, 4, 5, 1, 2 and 6 fell in that order. Then the wires at the annunciator would be changed as follows: From 3 to 1, 4 to 2, 5 to 3, 1 to 4, and 2 to 5; 6 would already be in its right place.
Another way is to commence by twisting together say the wires at No. 1 push. Then go to the annunciator and touch each of the push wires to No. 1 drop until it falls. Then connect it, untwist the wires at No. 1, push and connect it up. Proceed to No. 2 and so on until all the pushes have been connected in turn.
In some cases it is desired to answer back to the person calling, or to be able to call any person from the annunciator.
A circuit like [Fig. 58] answers the purpose of both annunciator call and return, or fire, call. This requires two wires from each room to the annunciator and a common return wire. By tracing out the circuit it will be seen that when a room push is pressed, the annunciator needle and bell indicate. And when one of the pushes near the annunciator is pressed, the corresponding room bell rings. The former circuit is from the push, along the common return wire, through bell and annunciator back to the push.
The fire call is from push up line to bell through bell along common return and through battery to the push.
The Western Electric single-wire system ([Fig. 59]) uses three-point pushes, two batteries and two return wires. Battery A is for the annunciator circuit and battery F for the fire, or return, call.
Fig. 59
In each room the top contact and push spring contact are normally together.
If one of the pushes below the annunciator is pressed, battery F is thrown in series with the bell in the room.
But when the room push is pressed its bell is cut out and the circuit becomes like an ordinary annunciator circuit.