(225 ILCS 705/7.12) (from Ch. 96 1/2, par. 712)

Sec. 7.12. At every mine where men are hoisted and lowered by machinery there shall be provided means of signaling to and from the bottom man, the top man and the engineer. The signal system shall consist of a tube, or tubes, or wire encased in wood or iron pipes, through which signals shall be communicated by electricity, compressed air or other pneumatic devices or by ringing a bell. When compressed air or other pneumatic devices are used for signaling, provision must be made to prevent signal from repeating or reversing.

(Source: Laws 1953, p. 701.)