the
cord leading from the desk stand and for the wires of the line
circuit. The condenser that is placed in series with the ringer is
also mounted in this same box. By employing two condensers, one in the
bell box large enough to transmit ringing currents and the other in
the base of the desk stand large enough only to transmit voice
currents, a duplication of condensers is involved, but it has the
corresponding advantages of requiring only two strands to the flexible
cord leading from the bell box to the desk stand proper.

[Illustration: Fig. 159. Microtelephone Set]

A form of desk-telephone set that is used largely abroad, but that has
found very little use in this country, is shown in Fig. 159. In this
the transmitter and the receiver are permanently attached together,
the receiver being of the watch-case variety and so positioned
relatively to the transmitter that when the receiver is held at the
ear, the mouthpiece of the transmitter will be just in front of the
lips of the user. In order to maintain the transmitter in a vertical
position during use, this necessitates the use of a curved mouthpiece
as shown. This transmitter and receiver so combined is commonly
called, in this country, the _microtelephone set_, although there
seems to be no logical reason for this name. The combined transmitter
and receiver, instead of being supported on an ordinary form of hook
switch, are supported on a forked bracket as shown, this bracket
serving to operate the switch springs which are held in one position
when the bracket is subjected to the weight of the microtelephone, and
in the alternate position when relieved therefrom. This particular
microtelephone set is the product of the L.M. Ericsson Telephone
Manufacturing Company, of Buffalo, New York. The circuits of such sets
do not differ materially from those of the ordinary desk telephone
set.

[Illustration: Fig. 160. Kellogg Common-Battery Desk Set]

[Illustration: Fig. 161. Dean Common-Battery Set]

Circuits of Common-Battery Telephone Sets. The complete circuits of
the Kellogg desk-stand arrangement are shown in Fig. 160, the
desk-stand parts being shown at the left and the bell-box parts at
the right. As is seen, but two conductors extend from the former to
the latter. A simplified theoretical sketch is also shown in the upper
right-hand corner of this figure.

The details of the common-battery telephone circuits of the Dean
Electric Company are shown in Fig. 1