Precautions with Shunt Motors.--With motors of this type, because of the large amount of self-induction in the shunt windings, it is important to note: 1, that in switching on the field magnet, the current may take an appreciable time to grow to its normal value, and 2, that in switching off, especially with quick break switches, high voltages are induced in the windings, which may break down the insulation. [Illustration: Fig. 749.--Monitor starter giving automatic start with knife switch control; designed for use with printing presses. It consists of a set of solenoids connected in series and so interoperating as to cut resistance out of the armature circuit of the motor as the apparatus it is driving comes up to speed. This type is for small motors or where no need arises for speed regulation; there is, therefore, no adjustment of speed possible aside from an actual change in motor conditions. At full speed the motor is directly across the main supply line. Fig. 750.--Monitor automatic starter, equipped with relay for push button control.] Ques. What provision is made so that the magnetizing current will have time to reach its normal value? Ans. The field connections are generally separated from the actual starter, and taken to the main switch, so that wherever the main switch is closed, the current flows through the field coils, before the starting lever is moved. Ques. How are the connections arranged to avoid excessive voltage in the windings due to self-induction? Ans. Generally the armature and field magnet circuits are placed in a closed circuit that is never opened. In other cases, in order that the rise of voltage may not injure the insulation when the shunt is opened, a special form of main switch is sometimes used which, before breaking from the supply, puts a non-inductive resistance across the shunt of the motor. This is known as a _flashing resistance_.