THE SPERRY GYRO-COMPASS IN SERVICE. 297 



In the daily operation of the compass the principal points to be observed 

 are : — 



(i) Avoid touching any part of the sensitive or gyroscopic element. 



(2) Keep the silver contacts and trolleys in good working order. 



(3) Keep the instruments and accessories clean and the circuits free 

 from grounds. 



The trials of the first eight instruments resulted in a contract for ten 

 more compasses, the first to be delivered on October i . The specifications 

 for the instruments on this contract are very rigid. They provide that each 

 set shall consist of a master compass, a motor-generator capable of generating 

 both 130 volt A. C. current for the driving of the gyro wheel and 20- volt D. C. 

 current for energizing the repeating system; a 40-ampere hour storage bat- 

 tery as auxiliary supply to the 20- volt system, arranged so that it floats on 

 the 20- volt system at all times; switchboards; synchronizing and cutout 

 switches, and four repeater compasses. The master compass is to contain an 

 automatic correction for all heads and to provide adjustment for changes in 

 speed and latitude. The level device, for showing the position of the merid- 

 ian independently of the compass card, is required. All parts of the instru- 

 ment are to be plainly marked to prevent any possible mistakes in assembling, 

 adjusting or reading. Trolleys and contacts are to be provided in duplicate 

 and must be so arranged as to be interchangeable. All gaskets to be unaf- 

 fected by heat or by oil with which they might come in contact. The instru- 

 ment must be provided with a means for automatically disconnecting the 

 gyro motor from the motor-generator in case of failure of the D. C. supply to 

 the motor-generator. This provision is made so that the motor-generator 

 will have no braking effect on the gyro motor in case of failure of the D. C. 

 supply. Provision is also made for an alarm bell so connected as to ring 

 continuously in case of failure of the D. C. supply. All repeaters are to be of 

 watertight construction and capable of immersion under a three-foot head 

 of water for three hours without indication of leakage. The binnacle re- 

 peaters are to be provided with flexible cable and with a watertight connec- 

 tion box outside of the repeater itself so that the repeater can be disconnected 

 and removed without the necessity of opening its case. All binnacle repeaters 

 are to be illuminated from behind the compass card. Repeaters are to be 

 furnished in binnacle type — that is, on a stand — or in wall type, for securing 

 to bulkheads, as required. Repeater compasses shall be required to follow 

 accurately the indications of the master compass at all rates of turning likely 

 to be met after installation. A synchronizing panel is to be provided which 

 shall be capable of setting any or all repeating compasses in exact agreement 

 with the master compass, as desired. All electrical parts of the instruments 



