screw _7_ the entire hook switch may be lifted out of the tube forming
the standard, the cords leading to the various binding posts being
slid along through the tube. By this means the connections to the hook
switch, as well as the contact of the switch itself, are readily
inspected or repaired by those whose duty it is to perform such
operations.

_Kellogg._ In Fig. 87 is shown a sectional view of the desk-stand hook
switch of the Kellogg Switchboard and Supply Company. In this it will
be seen that instead of placing the switch-hook springs within the
standard or tube, as in the case of the Western Electric Company, they
are mounted in the base where they are readily accessible by merely
taking off the base plate from the bottom of the stand. The hook lever
operates on the long spring of the group of switch springs by means of
a toggle joint in an obvious manner. This switch spring itself serves
by its own strength to raise the hook lever when released from the
weight of the receiver.

[Illustration: Fig. 87. Desk-Stand Hook Switch]

In this switch, the hook lever, and in fact the entire exposed metal
portions of the instrument, are insulated from all of the contact
springs and, therefore, there is little liability of shocks on the
part of the person using the instrument.

Conventional Symbols. The hook switch plays a very important part
in the operation of telephone circuits; for this reason readily
understood conventional symbols, by which they may be conveniently
represented in drawings of circuits, are desirable. In Fig. 88 are
shown several symbols such as would apply to almost any circuit,