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namo or circuit with certainty and rapidity, without in any manner affecting the operation of other dynamos or circuits (and such that it will be possible to connect two dynamos together by an arrangement of switches or combination of circuits.) (For switchboard connections see sees. 30 and 31, pp. 55 and 56.

64. circuits. (See p. 57, sec. 32.)

Series Arc System, Direct or Alternating . Current.

This contractor shall furnish, and, unless otherwise specified, install the following apparatus and material:

: arc light dynamo(s) (each) hav- 63- m^?"

ing a capacity of , c. p., ampere, volt arc lamps.

Each dynamo shall be provided with a regulator which shall automatically make the proper adjustments for all changes of load from no load to full load, the adjustments to be made in such a way as not to endanger any part of the dynamo, appliances or lamps, nor to cause any perceptible change in the balance remaining in operation; shall be of the latest and most efficient pattern; mounted on a base provided with an adjustable belt-tightener, so that the belt may be tightened while in operation; capable of operating under full load for consecutive hours without

increasing the temperature of any part, especially the armature, fields, and commutator, to such a degree as to endanger the insulation or decrease the efficiency of operation; shall have an insulation resistance of not less than ohms between all parts insulated from each other; shall be adapted to operate at such speed as will allow the use of high-speed, automatic-cut-off engines belted direct; shall be provided with efficient oiling devices; the armature shall be balanced both electrically and magnetically so that there will be no tendency to spring the shaft or to draw the armature toward either bearing so as to cause excessive friction and heating, and no vibration; especial attention shall be given the insulation, protection and separation of contacts, binding posts and bared surfaces having extreme differences of potential in order to minimize the danger of accidental shocks, crosses, or grounds under normal conditions of operation; the dy

namo(s) shall be so designed and automatically regulated that the power will be automatically proportioned to the number of lamps burning at any time.

(See Note: p. 48, sec. 23.)

There shall be provided with each dynamo, in addition to the automatic regulator required above, one ampere meter for indicating the current supplied by the dynamo and graduated to read amperes; one brush jig for trimming the brushes; one insulating baseframe, provided with rails and a suitable device for shifting the position of the dynamo to alter the belt tension; one main switch; one pair of lightning arresters; and for the general installation one testing set capable of measuring up to ohms.

(See p. 61, sec. 34.)

66. Founda Mods.

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single carbon )
double carbon V
triple carbon )

arc lamps of nominal candle-power.

Each lamp shall be provided with a switch by which it may be cut in or out of circuit; shall be regular in its feeding action; shall be free from hissing, flickering or naming when provided with proper carbons; shall contain an efficient device which shall automatically cut out a lamp for any reason defective, without interfering with the operation of the lamps remaining in circuit; and shall be simple, strong, and durable in its mechanical construction.

70Bc5?dJ:ar hanger boards for inside use, each

hanger board to contain a switch by which the lamp may be cut entirely out of circuit.

71. Hooas. waterproof hoods, complete with

hanger boards for outside use )
out-rigger attachments >
cross-suspension attachments )

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