Telegraph engineering : a manual for practicing telegraph engineers and engineering students (1922)
Hausmann, Erich, 1886- · New York : D. Van Nostrand Company · leaf 233
ir nearest street stations for 2l8 TELEGRAPH ENGINEERING the purpose of receiving instructions, may be incorporatedin police signal systems. In some cities police signalsystems utilize telephone instruments exclusively. Police signal boxes resemble fire-alarm boxes in thatthey include a mechanism… … Fig. 17. coil, properly connected together to form a telephone set.Fig. 17 represents a Gamewell 7-call police signal boxwith its outer door open, and Fig. 18 shows the same boxwith both outer and inner doors open to exhibit the variousparts. When a policeman has occasion to send any one of…
Telegraph
Internet Archive · Library of Congress · Public Domain Mark 1.0. Free to use for anything.
