[Illustration: Figs. 751 to 753.--Monitor control switches. Fig. 751, push button "start" and "stop" switch; fig. 752, safety lever control switch with "slow" and "fast" buttons for rotary printing presses. This device will upon pressure of the "start" button, set the machine in motion and bring it up to the predetermined speed, either as previously set by the starter limits or by the setting of the rheostat arm. The stop button projects some distance beyond any other portion of the device, in order that in case of emergency the operator may stop the machine merely by hitting the face of the switch with his open hand. The lever control switch, fig. 753, is similar in its action to the push button switch but combines two other features: locking point, and visual indication of the station from whence the press has been stopped. With the lever at the downward position, the press is locked and cannot be started from any other station. In order to make the press ready to start the lever must be raised to the central position. Thus a man may safely enter the press without delay by setting his station to the locked position, knowing that it cannot be started except by some one coming to that station and realizing that the press has been purposely locked. Also, by looking along the press, it is possible to tell from which station it has been locked, and proper action can be immediately taken. The safety control station is usually combined for use on large rotary presses with the "slow" and "fast" push buttons as shown in fig. 752. A pressure upon the fast or slow buttons will cause the press speed to be correspondingly accelerated or retarded, and this action will continue so long as the button is pressed. The press continues to run at the speed attained at the instant of releasing the button. Any speed may, therefore, be selected or changed to suit momentary requirements. This gives complete control excepting reversal which is not required of such a press.]