phone or telephone set. The receiver
will, as a rule, be designated as such, rather than as a telephone.
The term subscriber's station equipment will refer to the complete
equipment at a subscriber's station, and will include the telephone
set, the interior wiring, and the protective devices, together with
any other apparatus that may be associated with the telephone line and
be located within the subscriber's premises.

Classification of Sets. Telephones may be classified under two
general headings, magneto telephones and common-battery telephones,
according to the character of the systems in which they are adapted to
work.

_Magneto Telephone._ The term magneto telephone, as it was originally
employed in telephony, referred to the type of instrument now known as
a receiver, particularly when this was used also as a transmitter. As
the use of this instrument as a transmitter has practically ceased,
the term magneto telephone has lost its significance as applying to
the receiver, and, since many telephones are equipped with magneto
generators for calling purposes, the term magneto telephone has, by
common consent, come to be used to designate any telephone including,
as a part of its equipment, a magneto generator. Magneto telephones
usually, also, include local batteries for furnishing the transmitter
with current, and this has led to these telephones being frequently
called local battery telephones. However, a local battery telephone is
not necessarily a magneto telephone and _vice versa_, since sometimes
magneto telephones have no local batteries and sometimes local battery
telephones have no magnetos. Nearly all of the telephones which are
equipped with magneto generators are, however, also equipped with
local batteries for talking purposes, and, therefore, the terms
magneto telephone and local battery telephone usually refer to the
same thing.

_Common-Battery Telephone._ Common-battery telephones, on the other
hand, are those which have no local battery and no magneto generator,
all the current for both talking and signaling being furnished from a
common source of current at the central office.

_Wall and Desk Telephones._ Again we may classify telephones or
telephone sets in accordance with the manner in which their various
parts are associated with each other for use, regardless of what parts
are contained in the set. We may refer to all sets adapted to be
mounted on a wall or partition as _wall telephones_