Advantages of the Monocord Switchboard.
1. Small, compact, light weight.
2. Simple wiring.
3. Quickly installed.
4. Particularly suited for small central exchanges.
5. Units can be removed quickly, in case of trouble in interior circuits. Any unit can be removed without disturbing other units.
Common Faults and Remedies of the Magneto Telephone.
The most common trouble in telephone instruments are due generally to one of three causes. (1) Loose or dirty connections at the binding posts of the instrument, at the binding posts of the batteries, or in joints of the line wires, (2) exhausted, poor, or weak batteries, (3) crossed, open, or defective wires. These troubles, of course, do not include those arising from inferior or defective instruments. If the connections are dirty, corroded or greasy, scrape the wires and clean out the binding posts, then screw the wires firmly in place. If the telephone does not then work properly, examine the batteries and see whether they are run down or whether the zincs are eaten away. With wet batteries, it may be possible that the water has evaporated; in dry batteries, the zincs may be eaten through or the batteries may be otherwise defective. The simplest way to test a battery is to try a new battery, and see whether it will make the telephone work properly; if it does, the trouble is with the old battery. If the trouble is present after changing the battery, examine the line connections and the line outside; if any loose connections are found, correct them at once. When inspecting the line outside see that it does not touch anything except the insulators, and that it is neither crossed nor broken. On grounded lines—grounded lines are obsolete now in modern warfare on the account of the many means of detecting and picking up messages now employed; in fact the metallic circuit telephone lines are now used within a mile of the front lines except for messages which would be of no value to the enemy—examine the ground connections the first thing and see whether it is in good condition, and if a plate is used see that it is in moist ground. The frequent trouble with transmitters is the frying noise; that is usually caused by induction or static electricity, and may also be caused by loose connections.
| 1. | Open Line. | Effect: Cannot receive a call or get central. | |
| Test: Follow line with portable magneto test set and ring; if central gets ring, open is toward station or visa versa. | |||
| 2. | Open Battery. | Effect: Can hear and receive central call but cannot talk. | |
| 3. | Open primary winding. | Test: Strap out primary winding or transmitter with test receiver, and leaving the receiver off the hook at station, listen in either for click while moving switchhook up and down. If no noise be heard, battery circuit must be open, and circuit should be followed with test receiver, which will click loud where battery is found to be O. K. | |
| 4. | Open Transmitter. | ||
| 5. | Short Circuited Line. | Effect: No signal will show at magneto switchboard, and use of station instrument will be impaired and magneto will turn hard. | |
| 6. | Wet or short Circuited Instrum’t. | Test: Open line and ring; if magneto still turns hard open connections one at a time, where available throughout entire winding until magneto turns freely. | |
| 7. | Line crossed with another line. | Effect: Other talking heard on the line when the receiver is off the hook. | |
| Test: Ring magneto and with central’s help try to locate other party; then trace line. | |||
| 8. | Open secondary winding. | Effect: Can ring and hear central ring but cannot hear in receiver although can be heard. | |
| 9. | Open receiver. | Test: Strap test receiver across open part. | |
| 10. | Receiver diaphragm missing or badly dented. | ||
| 11. | Weak battery Cells. | Effect: Can hear well but cannot be heard clearly. | |
| Test: Use ampere meter and see if each cell be weak. | |||
| 12. | Open Bell. | Effect: Can talk and hear in receiver but bell does not ring. | |
| Test: Strap bell coils out with test receiver and listen in. | |||
| 13. | Open magneto Armature Winding. | Effect: Bell rings from central but does not ring when magneto handle is turned nor can central be called. | |
| Test: Ring with another magneto or test set. | |||
| 14. | Slight Short Circuit (escape) to Ground. | Effect: Can ring operator but cannot hear nor be heard clearly. | |
| Test: Open line, one line at a time, and follow circuit with test set. Escapes are due to wires touching damp walls, metal roof, or other grounded wire where insulation has been rubbed off. | |||