ine through the
third wiper of the connector and the coil _26_ of the called battery
supply relay. As a result, this subscriber receives proper talking
current through the coils _25_ and _26_, and this relay is operated by
the flow of this current. The operation of this called battery supply
relay merely shifts the connection of the rotary side of the calling
subscriber's line from its normal battery connection, to ground, and
thus the battery is placed straight across the calling subscriber's line
so as to supply talking current. This supply circuit to the calling
subscriber may be traced from the live side of the battery through the
winding _13_ of the calling battery supply relay and the winding of the
vertical relay to the vertical side of the line, and from the grounded
side of battery through the third side switch wiper in its third
position to the now closed pair of contacts in the called battery supply
relay through the coil _18_ of the calling battery supply relay and the
coil of the rotary relay to the rotary side of the line.

It will be noted that the system of battery supply is that of the
standard condenser and retardation coil scheme largely employed in
manual practice; and that aside from the coils through which the battery
current is supplied to the connected subscribers, there are no taps
from, or bridges across, the two sides of the talking circuit.

=Release after Conversation.= It remains now only to secure the
disconnection of the subscribers after they are through talking. When
the calling subscriber hangs up, the whole disconnection is brought
about, all of the apparatus, including connector, selectors, and line
switch, returning to normal. This is done by the back release system and
is accomplished in almost the same way as has already been described in
connection with the disconnect after an unsuccessful call. There is this
difference, however: after an unsuccessful call when the line called for
was found busy, the release was made while the connector side switch was
in its normal position. In the present case, the release must be made
with the connector side switch in its third position and with the
talking battery bridged across the metallic circuit rather than
connected between each limb of the line and ground. It must be
remembered that the calling battery supply relay, while traversed by
current during the conversation, is not magnetically energized because,
with the current flowing throu