1. Local circuit at fault.
(a) Battery, (b) connections or wiring, (c) transmitter, (d) primary coil.
2. Distant receiver out of order.
3. Home secondary coil short-circuited.
Operator's test:
Disconnect line and ground wires and connect binding-posts R and C with a piece of wire, thus short-circuiting the phone. Place the receiver to the ear and scratch gently with the finger-nail on the inside of the transmitter mouthpiece.
If this is distinctly heard, the local circuit and receiver are all right.
If no sound results, put the receiver to the ear, lower and raise hook lever, also open and close the two-way switch. If a distinct click is heard for each of these, the local circuit is all right but the transmitter may not be in good order and a report should be made.
If no sound results from above, make sure that the switch contact is good and no pivots are loose, that all contacts are good, that the connections at battery terminals are good with no green substance on the wires or posts, that the water in the jars is up to the prescribed point, about an inch from the neck of the cell, that the zincs and carbons are not touching, that the zincs are not eaten off, and that the zinc of one cell is connected to the carbon of the other, and that there are no crystals on the zincs and carbons.
The operator should correct any of these that he can, reporting the others.
For (2. Distant receiver out of order) the operator at the distant phone should try the tests above. If these give no sound in his receiver, he should try another receiver, if one is available. He may try a new cord or substitute two pieces of wire for it.
3d. Can neither hear nor be heard.
Analysis:
This indicates general trouble:
1. In the phones.
2. In the line.
Operators' test:
Go over the phone carefully, looking for poor contacts, as when an insulated wire is put in the binding-posts, binding-posts not screwed down tight, ends of wires passing through post touching other parts, contacts at cells and condition of cells as noted before. Disconnect the line and ground wires and test out phones as indicated. See that ground wire is in the middle post. If there are fuses in the line, see that they are not burned out. If no trouble is found to exist when the line is disconnected, report line out of order.