condition, as shown in Fig. 196.

[Illustration: Fig. 198. Details of Latching Relay Connections]

As has been stated, the windings _7_ on the line relays are the
unlatching windings. In Figs. 196 and 197, for the purpose of
simplicity, these windings are not shown connected, but as a matter of
fact each of them is included in series in the continuous limb _L_ of
the line. This would introduce a highly objectionable feature from the
standpoint of talking over the line were it not for the balancing
coils _7_^{1}, each wound on the same core as the corresponding
winding _7_, and each included in series in the limb _R_ of the line,
and in such direction as to be differential thereto with respect to
currents passing in series over the two limbs of the line.

The windings _7_ are the true unlocking windings, while the windings
_7_^{1} have no other function than to neutralize the inductive
effects of these unlocking windings necessarily placed in series in
the talking circuit. All of these windings are of low ohmic
resistance, a construction which, as has previously been noted, brings
about the desired effect without introducing any self-induction in
the line, and without producing any appreciable effect upon the
transmission. A study of Fig. 198 will make clear the connections of
these unlocking and balancing windings at each station.

The statement of operation so far given discloses the general method
of building up the line in sections in order to choose any party and
of again breaking it up into sections when the conversation is
finished. It has been stated that the same operation which selects the
party wanted also serves to give that party the use of the line and to
lock the others off. That this is true will be understood when it is
stated that the ringer is of such construction that when operated to
ring the subscriber wanted, it also operates to unlatch a set of
springs similar to those shown in Fig. 194, this unlatching causing
the proper connection of the subscriber's talking circuit across the
limbs of the line, and also closing the local circuit through his
transmitter. The very first motion of the bell armature performs this
unlatching operation after which the bell behaves exactly as an
ordinary polarized biased ringer.

[Illustration: Fig. 199. Broken-Back Ringer]

The construction of this ringer is interesting and is shown in its two
possible positions in Fig. 199. The group of springs carried on its