The provisions of <cite data-path="3">this subtitle</cite> shall not apply to journeymen electricians or apprentices while such journeymen or apprentices shall be practicing their trade of journeymen electrician or apprentice, nor to any electric light company, electric railway company, steam railway company, telegraph or telephone company doing such work in its own buildings, upon its own plants. P.L.L., 1915, §663Q 1927, §663Q 1930, §663Q 1938, §795 1949, §495 1969, §3-18 1906, ch. 244, sec. 17