This is the same as the method of starting a motor, that is, _by variation of resistance in armature circuit_, but it should be noted that when this method is used for speed regulation, _a speed regulating rheostat should be used instead of the ordinary starting box_, because the latter, not being designed for the purpose, _will overheat and probably burn out_. [Illustration: Fig. 755.--Monitor printing press controller. It provides variable speed and other control features required in the operation of large rotary presses, such as those used for printing newspapers. From any one of various stations similar to the one illustrated in fig. 753, located at all desirable places about the press, the latter may be started, stopped, accelerated, slowed down or locked. It differs from other types of printing press controller in that the solenoid has an overall maximum pull of less than one inch and does not actuate the main line current directly but through pilot circuits, which in turn, operate flapper switches; there are no sliding contacts. At the control stations, the operator can distinguish the accelerating button from the retarding button by the sense of touch and obviously he can in the same manner ascertain the position of the lever. The position of the lever whether at start, stop or safety, can be readily observed at a distance. When the lever of either control station is placed at stop, the current is disconnected from the motor and a powerful dynamic brake brings the press to rest without delay and without shock or harmful strain. The start will always be made with all resistance in the armature circuit, and with full field, and should the current supply fail, the controller will release and open the circuit to the motor. This controller will give a speed range as low as 10% of normal speed by armature resistance and, by field control, any increase within the speed of the motor.] Ques. Describe the second method. Ans. This method of regulating the speed of a series motor is shown in fig. 757. The current through the armature will flow through all the field windings when the position of the switch lever S, is on contact 4, and the strength of the field will be the maximum. By moving the arm to contact 3, 2, etc., sections of the field winding are cut out, thus reducing the strength of field and varying the speed. [Illustration: Fig. 756.--Speed regulation of shunt motor by variable resistance in the armature circuit.] Ques. How does the speed vary with respect to variation of field strength? Ans. Decreasing the field strength of a motor increases its speed, while increasing the field strength decreases the speed.