ected with one end of this cord circuit and a short line having a
low-resistance series ringer be connected with the other end, then a
station on the long line may have some difficulty in throwing the
clearing-out drop, because of the low-resistance shunt that is placed
around it through the short line and the low-resistance ringer. In
other words, the clearing-out drop is shunted by a comparatively
low-resistance line and ringer and the feeble currents arriving from a
distant station over the long line are not sufficient to operate the
drop thus handicapped. The advent of the various forms of party-line
selective signaling and the use of such systems in connection with
magneto switchboards has brought in another difficulty that sometimes
manifests itself with this type of cord circuit. If two ordinary
magneto telephones are connected to the two ends of this cord circuit,
it is obvious that when one of the subscribers has hung up his
receiver and the other subscriber rings off, the bell of the other
subscriber will very likely be rung even though the clearing-out drop
operates properly; it would be better in any event not to have this
other subscriber's bell rung, for he may understand it to be a recall
to his telephone. When, however, a party line is connected through
such a cord circuit to an ordinary line having bridging instruments,
for instance, the difficulty due to ringing off becomes even greater.
When the subscriber on the magneto line operates his generator to give
the clearing-out signal, he is very likely to ring some of the bells
on the other line and this, of course, is an undesirable thing. This
may happen even in the case of harmonic bells on the party line, since
it is possible that the subscriber on the magneto line in turning his
generator will, at some phase of the operation, strike just the proper
frequency to ring some one of the bells on the harmonic party line. It
is obvious, therefore, that there is a real need for a cord circuit
that will prevent _through ringing._

One way of eliminating the through-ringing difficulty in the type of
cord circuit shown in Fig. 281 would be to use such a very low-wound
clearing-out drop that it would practically short-circuit the line
with respect to ringing currents and prevent them from passing on to
the other line. This, however, is not a good thing to do, since a
winding sufficiently low to shunt the effective ringing current would
also be too low for good t