Selection of Starters and Regulators.--Unsatisfactory operation of these devices is, in nearly all cases, due to lack of precaution in selecting the proper piece of apparatus for the work to be done. One of the commonest errors is to select a rheostat of insufficient capacity. If the current required to operate the motor at full speed with no resistance in circuit be greater than the rated capacity of the rheostat, overheating of the resistance will result. An increase in temperature even to a point where the hand cannot be held on the enclosing case need cause no apprehension, but should the resistance become red hot it indicates that the apparatus is being worked far beyond its capacity, and the load on the motor should be reduced or a regulator of greater capacity substituted. If the current required to operate the motor at full speed with no resistance in circuit be less than the rated capacity of the rheostat no overheating will occur, but it will not be possible to secure the full 50 per cent. speed reduction the rheostat is designed to give with all resistance in circuit. [Illustration: Fig. 768.--Various sizes of Watson commutator. The segments are punched from hard drawn copper strip and are insulated from each other and the core by amber mica, of hardness corresponding to that of the copper in order that the wear of mica and copper may be uniform. The segments are assembled in a ring under great pressure and are repeatedly heated and tightened, being finally secured and rigidly locked together.] In ordering a starter or regulator, the manufacturer should be furnished with the following information: 1. Horse power of motor with which speed regulator will be used; 2. Voltage of motor; 3. Winding of motor, whether series, shunt, or compound wound; 4. Nature of the machine which motor is to operate; 5. Normal rated speed of motor to be used; 6. Maximum speed at which it is desired to operate the motor; 7. Minimum speed at which it is desired to operate the motor; 8. Whether controller will ever be required to reverse direction of motor or to operate it in one direction only; 9. If reversible controller be desired, whether or not full range of speed control is required in both directions; 10. Whether the regulator shall be equipped with any of the following devices: no voltage release, overload release, knife switch, fuses; 11. Whether button contacts or renewable contact segments are preferred; 12. Giving, also, if possible, the resistance of the shunt field cold, and the shunt field current at the maximum speed required. If this cannot be ascertained, give horse power, voltage, normal speed, maximum speed required, serial number of motor and name of manufacturer.