Excerpt from The Technograph, Vol. 33: November, 1920
In spite oi' the fact that line circuits often pass through the contacts of three or more relays, this ati'ects the safety of the circuit but little, as the con tacts of up-to-date relays offer very little resistance to the passage of current. The contacts of such re lays, of which there are usually four, are made of large silver and graphite contact pieces which are held tightly together by the magnetic pull of the large operating coils. In addition to this, it has become the general custom to provide the most im portant circuits with two relay contacts in parallel, provided of course, that the contacts are available. The modern signal relay is a verv well constructed piece of mechanism and when once adjusted holds its adjustment almost indefinitely. Incidentally, it is the general practice to seal all relays to protect them from tin-authorized adjustment. These relays are made and adjusted with such uniformity that after they have been installed they show not more. Than one to two percent of variation in the amount of current required to operate them.
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