[Illustration:  Fig. 156.  Common-Battery Desk Set]

[Illustration:  Fig. 157.  Bell for Common-Battery Desk Set.]

The Kellogg Switchboard and Supply Company is one which places all the parts, except the polarized ringer and the associated condenser, in the desk stand itself.  In Fig. 156 is shown a bottom view of the desk stand with the bottom plate removed.  In the upper portion of the circle of the base is shown a small condenser which is placed in the talking circuit in series with the receiver.  In the right-hand portion of the circle of the base is shown a small impedance coil, which is placed in series with the transmitter but in shunt relation with the condenser and the receiver.

[Illustration:  Fig. 158.  Bell for Common-Battery Desk Set]

In Figs. 157 and 158 are shown two views of the type of bell box employed by the Kellogg Company in connection with the common-battery desk sets, this box being of pressed-steel construction and having a removable lid, as shown in Fig. 158, by which the working parts of the ringer are made readily accessible, as are also the terminals for 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.