combined drops and jacks and, therefore, equipped for fifty subscribers’ lines.  The drops and jacks are mounted in strips of five, and arranged in two panels.  The clearing-out drops, of which there are ten, are arranged at the bottom of the two panels in a single row and may be seen immediately above the switchboard plugs.  There are ten pairs of cords and plugs with their associated ringing and listening keys, the plugs being mounted on the rear portion of the shelf, while the ringing and listening keys are mounted on the hinged portion of the shelf in front of the plugs.

[Illustration:  Fig. 296.  Details of Drop, Jack, Plug, and Key Arrangement]

[Illustration:  Fig. 297.  Cross-Section of Upright Switchboard]

A better idea of the arrangement of drops, jacks, plugs, and keys may be had from an illustration of a Dean magneto switchboard shown in Fig. 296.  The clearing-out drops and the arrangement of the plugs and keys are clearly shown.  The portion of the switchboard on which the plugs are mounted is always immovable, the plugs being provided with seats through which holes are bored of sufficient size to permit the switchboard cord to pass beneath the shelf.  When one of these plugs is raised, the cord is pulled up through this hole thus allowing the plug to be placed in any of the jacks.

The key arrangement shown in this particular cut is instructive.  It will be noticed that the right-hand five pairs of plugs are provided with ordinary ringing and listening keys, while the left-hand five are provided with party-line ringing keys and listening keys.  The listening key in each case is the one in the rear and is alike for all of the cord pairs.  The right-hand five ringing keys are so arranged that pressing the lever to the rear will ring on the answering cord, while pressing it toward the front will cause ringing current to flow on the calling plug.  In the left-hand five pairs of cords shown in this cut, the pressure of any one of the keys causes a ringing current of a certain frequency to flow on the calling cord, this frequency depending upon which one of the keys is pressed.

[Illustration:  Fig. 298.  Cord Weight]

An excellent idea of the grouping of the various pieces of apparatus in a complete simple magneto switchboard may be had from Fig. 297.  While the arrangement here shown is applicable particularly to the apparatus of the Dean Electric Company, the structure indicated is none-the-less generally instructive, since it represents good practice in this respect.  In this drawing the stationary plug shelf with the plug seat is clearly shown and also the hinged key shelf.  The hinge of the key shelf is an important feature and is universally found in all switchboards of this general type.  The key shelf may be raised and thus expose all of the wiring leading to the keys, as well as the various contacts of the keys themselves, to inspection.

[Illustration:  Fig. 299.  Magneto Switchboard, Target Signals]