The following is from "Technical and General Instruction Pertaining to Western Union Telegraph Business, Circuit Rules, Signals, Tariffs, Accounts, Cables, Press Dispatches, and Train Orders, with Questions, Answers, and Forms Used in Valentines' School of Telegraphy". Published in 1898, copyright 1888 by the Valentine Brothers.
This is a very important subject and should have its full share of attention.
Relay.-- The adjustments of the relay are two kinds. First, the adjustment of the extent of to an fro movements of the armature; second, the adjustment of the opposing action of the electro-magnet and of the retracting spring upon the armature lever. The first mentioned adjustment is effected by a screw top at the top of the vertical brass frame that supports the front end of the electromagnet. The play between the two platinum points of the relay should never exceed one-thirty-second of an inch, and when the movement of the lever is feeble the play should be made as small as possible. The second adjustment necessitates considerable skill and judgment on the part of the operator. When the action of the electro-magnet is very strong and the armature does not recede promptly when released, the tension of the spiral spring must be increased. In some cases the increased tension will not be sufficient, and the remedy is to lessen the action of the electro-magnet upon the armature by removing the former to a greater distance from the latter, which is accomplished by turning the screw at the rear of the electro-magnet.
Residuary Magnetism sometimes causes the armature to "stick," which interferes with the local circuit only. If the platinum point on the armature lever, and the one against which it strikes, are carefully cleaned with emery paper or a fine platinum file, removing as little platinum as possible, and the armature is adjusted so as not to touch the ends of the magnet, so "daylight" can be seen between them, then if it continues to stick, it may often be remedied by reversing the direction of the current through the relay, as stated below concerning the sounder.
In rainy weather, or when insulation is defective from any cause, the cores of the relay must be withdreawn farther from the armature and great care exercised in adjusting, as almost constant adjustment is required as such times.
Be careful in adjusting the axis of the armature lever on the relay, and the sounder, and the trunnion of the key, not to fasten the screws so tight as to prevent a free, unimpeded motion of the lever, nor to leave them so loose as to permit more than slight lateral or side motion.
Key.-- The key should never be opened without carefully adjusting the relay to be sure that no other office is using the line.
When the faces of the platinum points become oxidized or "dirty" from the repeated action of the electric spark, or other causes, the key is liable to "stick," as this interferes with both sending and receiving, the faces should be cleaned by carefully rubbing them with a fine platinum file, or hard, clean emery paper should be drawn between them. If the key is adjusted close and is used constantly, the points must be cleaned often. A "dirty" key prevents the perfect opening and closing of the circuit, and is a fruitful source of annoyance all along the line. The circuit closer should be kept in a condition to make a perfect closing of the circuit.
Sounder.-- The spiral spring should be adjusted in proportion to the strength of the battery, i.e., so that the effect of the current will overcome the force of the spring. If the tension is too great the armature cannot respond to the attraction of the magnet; but if the spring is not drawn sufficiently tight, the lever will not be released quickly back against the top screw when no current is passing around the cores.
The side screw which holds the axis of the armature lever, should be so adjusted as to give the armature lever freedom of motion without too much lateral movement.
When once properly adjusted, if the local battery is kept up, the sounder will need no further adjustment.
After long use and proper adjustment, if a sounder seems to "stick" or gives indications of residual magnetism, reverse the course of the current 'round the cores by changing the wires in the screw posts. This applies also to the relay.
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