Consequently no sound is heard in a
telephone, T, inserted in the line-circuit. Neither the currents which
start from one end nor those which start from the other will affect
the telephones inserted in the line. And, if these currents do not
affect telephones in the actual line, it is clear that they will not
affect telephones in neighboring lines. Also the telephones so
inserted in the main line might be used for speaking to one another,
though the arrangement of the telephones in the same actual line would
be inconvenient. Accordingly M. Van Rysselberghe has devised a further
modification in which a separate branch taken from the telegraph line
is made available for the telephone service. To understand this
matter, one other fact must be explained. Telephonic conversation can
be carried on, even though the actual metallic communication be
severed by the insertion of a condenser. Indeed, in quite the early
days of the Bell telephone, an operator in the States used a condenser
in the telegraph line to enable him to talk through the wire.
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