Cyclopedia of architecture, carpentry, and building : a general reference work ... (1907)
American School of Correspondence · Chicago : American Technical Society · leaf 373
Fig. 24, This type of lamp is used ex-tensively only on alternating-current circuits at a frequency ofabout GO cycles, and preferablyat 220 volts, as the efficiency isbetter at this voltage, due to lessenergy being consumed in theballast. Series lamps, and lampsoperated on direct current, are still…
Architecture · Building · Carpentry
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