MISSOURI'S NEW STATE CAPITOL-NORTH VIEW. (See page 244.)

Otis No. 6 Magnet Controller General description of No. 6 controller: Fig. 1 shows the general arrangement of the Otis No. 6 magnet controller. This is a later type than the G. S. controller previously described and although its mechanical details are quite different, its principle of operation is almost identical. The resistance, which is usually in the form of cast-iron grids for controllers of large capacity, is arranged behind the board and does not appear in the figure. The various switches are marked A', B', C', 1, 2, 3, 4. 5. Switches A', B', C', and 1 are operated by the car-controlling switch; the other switches operate automatically. Whenever a switch, for example C', operates, its plunger c is drawn up, thus bringing the copper disks d, d' up against the contact fingers f,f'. When a switch is de-energized, its plunger drops and the disks make contact with the lower fingers where any are provided. When a disk is drawn up, it first makes contact with the auxiliary carbon contacts x, and as it is pulled up still further, it bears against a copper contact on a finger hinged at the same point as the finger that carries the carbon contact. When a disk drops, it first breaks contact at the copper surfaces, and the final break takes place between the copper and the carbon terminal, so that there is no danger of sticking. The carbon pieces are threaded, so as to prevent their working loose and sliding through the holders. The plung

ers, with their contact plates are free to revolve, and the motion of the switch

gradually works them around so that whatever burning takes place is spread around the whole disk instead of in one place only. Switches 2, 3, 4 and 5 operate automatically, one after the other, and the voltage at which they operate is adjusted partly by regulating the initial position of the plunger by means of the adjustable stops h, and partly by inserting a resistance in series with each solenoid. The main fuses are shown at k, k; they are of the enclosed type. The small knife switches shown. at c are used for cutting off the carcontrolling switch, so that the motor cannot be started from the car. Push

buttons p u and p d are used to allow the motor to be operated from the board. These devices are very useful trouble, but under ordinary working when tests are being made to locate conditions they are not in use. Switches A' and B' control the direction of mo

tion of the car. When A' operates, the cends. Switch C' closes and opens the car descends, and B' operates, it as

main circuit.

No. 6 Car-Controlling Switch: Fig. 2 shows the car-controlling switch used with the No. 6 controller, the cover be ing removed in order to show the working parts. The operating handle is shown at h, and it normally occupies the central, or off, position. When moved to the left, the car ascends, and when moved to the right, it descends.

The arm carries a contact arc b that makes contact with the fingers 1, 2, 3, 4, etc., when the handle is moved from its central position. The arc b is of such a length that when the handle is moved to its extreme position in either direction, it makes contact with all four fingers on the side to which it is moved. The handle h is held at the central position by means of a spiral spring s, so that if the operator releases the handle, it at once returns to the off position. When the handle is at the off position, the projecting rim k rests in a notch in the plate p, and in order to move the handle, it must first be pulled out against the action of a spring. Insulating pieces i are inserted between the fingers, as shown, in order to avoid shortcircuiting.

Connections for No. 6 Magnet Controller: Fig. 3 shows the connections of the No. 6 controller. In this diagram the positions of the switches, resistances, and motor armature and field windings have been arranged so as to make the diagram simpler and easier to follow than if the various parts were located in the same position that they occupy on the controller. The connections are, however, the same as used on the controller shown in Fig. 1, and corresponding switches are lettered alike. The operation is on the whole very similar to that of the G. S. controller. Terminal x of the operating circuit is connected to the line and terminal y to the line. By throwing the small switch c down into the dotted position c", the car cannot be operated from P'. Switch m is normally open, but it can be thrown so as to connect t and d or t and u. If c is thrown down to the position c" and m is thrown. down so as to connect t and d, magnet A' is energized, and if push button pd is then pressed, current will flow through the coil of C' and the elevator will move down. If m be thrown up so as to connect m and u and button p u pressed, switches B' and C will be operated and the car will move up. In other words, the small switches and push buttons allow the machine to be operated from the controller while the switch P' is cut off.

indicated by the arrows through the coil of B' to the negative terminal y. Note that this current passes through the small contacts 1 and 2 of switch A', so that unless switch A' is down, B' cannot be drawn up, and it is impossible, therefore, for both switches to be drawn up together. When z is moved still farther so as to bring it in contact with the finger p u, a current is set up through the operating circuit, which includes the solenoid of switch C. This current may be traced as follows: x-c

c'-p u- p u to contact p u on stop motion switch-p-P-through solenoid of C'-65-4-3 to line. This current operates C', which closes the main circuit, releases. the brake, and connects the shunt field and extra field across the armature. The various paths of the current are indicated by the arrows, bearing in mind that B' and C' are now up. A powerful magnet field is provided by the series coils, and as the motor comes up to speed, switches 2, 3, 4, and 5 operate, thus short circuiting the resistance. and the series field. For example, when switch 2 closes, the main current passes from terminal R, to R2, thus short-circuiting the first two resistance sections. When the handle of P' is advanced so that z makes contact with finger fu, switch No. 1 is operated. This breaks

ance r, to the negative side of the circuit. This resistance is inserted to prevent undue heating of C' and also to save current. Also, when switch 5 is operated, the current through the coils. of 2 and 3 is cut off, thus preventing these coils from heating and cutting off the current necessary to energize them. When the core of 2 drops, contact is established again between points 3 and 4, but in the meantime it has been broken between 5 and 6, so that the current through C' still flows through the resistance rp. The coils in 1, 4 and 5 have considerable resistance in series with them and do not overheat.

It is,

of course, necessary that these three should remain up while the motor is running, otherwise the extra field resistance, and series fields would not be cut out, while with switches 2 and 3 it is not necessary that they should remain up after sections 2 and 3 of the resistance have been cut out. The voltage at which switches 2, 3, 4 and 5 operate is adjusted by means of the resistances r, r1, r, switch 2 having no resistance and, therefore, operating at the lowest voltage. When P' is moved to the right, switch A' is energized and the elevator descends because the direction of the current through the armature is reversed, while that in the fields remains the same as before. The action of the stop-motion switch is the same as in connection with the G. S. controllor and needs no special description.

Operation of No. 6 Controller on Stopping: When P' is moved back, contact is first broken with the f u finger. This drop switch 1 and cuts one section of resistance into circuit as well as connecting points R. and M, thus cutting in the extra field. When contact is broken with finger p u, all the resistance is cut in and the main circuit opened because switch C' is dropped. In fact, the switches 2, 3, 4 and 5 will likely operate before contact is actually broken between z and p u, if the operating switch is not moved too quickly, because the cutting in of the first section of the resistance and the extra field will lower the speed and thus cut down the E.M.F. applied to coils 2, 3, 4 and 5. When C' drops, the brake is applied because the circuit through the brake magnet is opened. When the main cir