718 LAWS OF MARYLAND. [CH. 307

FIVE RINGS or WHISTLES: Accident in Mine—Send
Stretcher.

Additional signals may be added by agreement between the
operator and the district mine inspector, but such signals must
be printed together with the code herein provided, on large
posters or cards, and displayed in the engine room and at all
points where used.

SEC. 108. Any person who shall deface, pull down, destroy,
interfere with or disregard any notice board, signal or warn-
ing in any such mine, or knowingly damage any signal or
communication system, or knowingly give or cause to be
given any wrong signal within or about such mine, or deface
or destroy any general or special rules or mining laws, or
knowingly destroy, falsify or remove or conceal any record
or report herein required to be made and kept, shall be guilty
of a misdemeanor.

CHAPTER X|VI—Electricity in Mines and Mining.

SEC. 109. All electric systems employed in, at, or about
.any mine in this State shall be installed, extended and/or
operated subject to reasonable regulation and supervision by
the Bureau; Provided, That in making and amending such
regulations, due regard shall be paid to commercially accepted
and approved underwriters' regulations, and to electric regu-
lations recommended by the United States Bureau of Mines.

SEC. 110. The various electric systems shall be classified by
voltages as follows: All such systems wherein the maximum
voltage cannot exceed 300 volts shall be known as "low volt-
age" systems. All such systems wherein the voltage exceeds
300 volts but the maximum whereof cannot exceed 650 volts
shall be known as "medium voltage" systems. All such sys-
tems wherein the voltage can exceed 650 volts shall be known
as "high voltage" systems.

SEC. 111. Every six months the operator of every coal
mine in which any electric system exists shall make an "elec-
tric system map" of such mine, which shall show by distin-
guishing colors and signs upon a good exact reproduction of
the map of such mine as hereinbefore required to be made, as
the same has been extended to date, such electric system, in
such detail as may be prescribed by the Bureau. Identical
copies of such electric system map shall be kept in the office