igures do not show the
intermediate frame.

The two terminals _4_ and _5_ of the intermediate frame, besides being
connected to the tip and sleeve springs of the answering jack, are
connected to the contacts of the cut-off relay, and thence through the
coils of the line relay to ground on one side and to battery on the
other. Thus the line relay and battery are normally included in the
circuit of the line. The contact _6_ on the intermediate distributing
frame, besides being connected to the test thimble of all the jacks, is
connected through the coil of the cut-off relay to ground, thus
establishing a path by which current is supplied to the cut-off relay
when connection is made to the line at any jack. There is another
contact _7_ on the intermediate distributing frame which merely forms a
terminal for joining one side of the line lamp to the back contact of
the line relay.

_Functions of Distributing Frames._ Since the line circuit thus far
described in connection with Fig. 348 is exactly the same as that of
Fig. 345 in its electrical connections, it becomes obvious that the main
and intermediate distributing frames play no part in the operation of
the circuit any more than a binding post of a telephone plays a part in
its operation. These frames carry terminals for facilitating the
connection of the various wires in the line circuit and, as will be
shown later, for facilitating certain changes in the line connection.

[Illustration: Fig. 348. Line Circuit No. 1 Board]

Remembering that the dotted lines in Fig. 348 indicate jumper wires of
the main and intermediate distributing frames, and that these are in the
nature of temporary or readily changeable connections, and that the full
lines, whether heavy or light, are permanent connections not readily
changeable, it will be seen that the wires leading through the multiple
jacks of a certain line are permanently associated with each other, and
with certain terminals on the main distributing frame and certain other
terminals on the intermediate distributing frame. It will also be seen
that the line lamp and the answering jack, together with the cut-off
relay and line relay, are permanently associated with each other and
with another group of terminals _4_, _5_, _6_, and _7_ on the
intermediate distributing frame. It will also be apparent that by
changing the jumper wires on the main frame, any outside line may be
connected with any different set of line switchboard