1. When used in this section "signalman" means:a. A telegraph or telephone operator reporting trains to another office or to a train dispatcher;b. A telegraph or telephone leverman who manipulates interlocking machines in railroad yards or on main tracks on the lines;c. A train dispatcher whose duties pertain to the movement of cars, engines or trains, by telegraph or telephone in dispatching or reporting trains or receiving or transmitting train orders.2. When used in this section "railroad" means: any portion of a surface, subway or elevated railroad situated wholly or partly in this state and operated by a corporation or receiver on which portion at least twenty freight trains on the average or nine regular passenger trains pass each way in every twenty-four hours.3. No signalman shall be employed on any railroad for more than eight hours in any day except in cases of extraordinary emergency caused by accident, fire, flood or danger to life or property and he shall be paid for each hour of such overtime at least one-eighth of his daily compensation.4. Every signalman and every towerman or gateman performing duties similar to those of a signalman, who is employed for eight hours or more every day shall be allowed at least two days of rest of twenty-four hours each in every calendar month with the regular compensation, except in cases of extraordinary emergency caused by accident, fire, flood, or danger to life or property, when in addition to his regular compensation he shall be paid for every hour so employed at least one-eighth of his daily compensation.5. The provisions of this section shall not apply to employees engaged in interstate commerce.