mployers,
who had come to recognize his marked genius, set him to work again on
the switchboard. He was placed in charge of the switchboard department
of the Western Electric Company, the concern which manufactures the
apparatus for the telephone company. The switchboard, as we have
seen, was Carty's first love, and again he pointed the way to great
improvements. Most of the large switchboards of that time were
installed under his direction, and they were better switchboards than
had ever been known before.

Up to this time it had been thought necessary to have individual
batteries supplying current to each line. These were a constant source
of difficulty, and Carty directed his own attention, and that of his
associate engineers, to finding a satisfactory solution. He sought a
method of utilizing one common battery at the central station and the
way was found and the improvement accomplished.

Though the telephone circuits were now protected from the earth,
telephone-users, at times when the lines were busy, were still
troubled with roarings and strange cross-talk. Though busy with the
many engineering problems which the telephone heads had assigned to
him, Carty found time for some original research. He showed that the
roarings in the wires were largely caused by electro-static induction.
In 1889 he read a paper before the Electric Club that startled the
engineers of that day. He demonstrated that in every telephone circuit
there is a particular point at which, if a telephone is inserted, no
cross-talk can be heard. He had worked out the rules for determining
this point. Thus he had at once discovered the trouble and prescribed
the cure. Of course it could not be expected that the sage experts
would all agree with young Carty right away; but they were forced to
in the end, for again he was proved right.

By 1901 Carty was ready with another invention which was to place the
telephone in the homes of hundreds of thousands who, without it, could
scarcely have afforded this modern necessity. This was the "bridging
bell" which made possible the party line. By its use four telephones
could be placed on a single line, each with its own signal, so that
any one could be rung without ringing the others. Its introduction
inaugurated a new boom in the use of the telephone.

Theodore Vail had resigned from his positions with the telephone
companies in 1890 with the determination to retire from business. But
when the panic of 1