Fig. 339. Face of Magneto Multiple Switchboard]

=Modern Magneto Multiple Board.= Coming now to a consideration of modern
magneto multiple switchboards, and bearing in mind that such boards are
to be found in modern practice only in comparatively small installations
and then only under rather peculiar conditions, as already set forth, we
will consider the switchboard of the Monarch Telephone Manufacturing
Company as typical of good practice in this respect.

[Illustration: Fig. 340. Monarch Magneto Multiple Switchboard Circuits]

_Line Circuit._ The line and cord circuits of the Monarch system are
shown in Fig. 340. It will be seen that each jack has in all five
contacts, numbered from _1_ to _5_ respectively, of which _1_ and _4_
are the springs which register with the tip and ring contacts of the
plug and through which the talking circuit is continued, while _2_ and
_3_ are series contacts for cutting off the line drop when a plug is
inserted, and _5_ is the test contact or thimble adapted to register
with the sleeve contact on the plug when the plug is fully inserted. The
line circuit through the drop may be traced normally from one side of
the line through the drop coil, thence through all of the pairs of
springs _2_ and _3_ in the jacks of that line, and thence to spring _1_
of the last jack, this spring always being strapped to the spring _2_ in
the last jack, and thence to the other side of the line. All the ring
springs _1_ are permanently tapped on to one side of the line, and all
of the tip springs _4_ are permanently tapped to the other side of the
line. This system may, therefore, properly be called a branch-terminal
system. It is seen that as soon as a plug is inserted into any of the
jacks, the circuit through the drop will be broken by the opening of the
springs _2_ and _3_ in that jack. The drop shown immediately above the
answering jack is so associated mechanically with that jack as to be
mechanically self-restored when the answering plug is inserted into the
answering jack in response to a call. The arrangement in this respect is
the same as that shown in Fig. 259, illustrating the Monarch combined
drop and jack.

_Cord Circuit._ The cord circuit needs little explanation. The tip and
ring strands are the ones which carry the talking current and across
these is bridged the double-wound clearing-out drop, a condenser being
included in series in the tip strand between the two drop windings in
the mann