. Western electrician . cale of the Edison carbontransmitter and the Blake microphone placed telephonyupon such a practical basis that its progress became as- I. Read before the Institution of Electrical Engineers, London*a nuary 24, 1S95. sured. It was the microphonic era when was commencedthat activity in telephone exchange work which necessi-tated attention being given to switching mechanism. In addition to the public exchange system every largetelegraph office was the center of numerous lines, whichwere connecled together as required by means of a switch-board. An illustration of part of a
. Western electrician . cale of the Edison carbontransmitter and the Blake microphone placed telephonyupon such a practical basis that its progress became as- I. Read before the Institution of Electrical Engineers, London*a nuary 24, 1S95. sured. It was the microphonic era when was commencedthat activity in telephone exchange work which necessi-tated attention being given to switching mechanism. In addition to the public exchange system every largetelegraph office was the center of numerous lines, whichwere connecled together as required by means of a switch-board. An illustration of part of a well-known telegraphswitchboard shown to the meeting consists of vertical andhorizontal bars, the vertical bars being the lines, the hori-zontal bars providing the means of connecting any onevertical line with another by inserting plugs. The verticallines terminate in springs resting on contacts. A telegraphinstrument can be looped into, circuit by a double-contactplug inserted between the spring and its contact. These. FIG. 2. THREE-PHASE WIRING AND LIGHTING FIXTURES IN CONCORD, N. H.—CONNECTIONS IN REAR OF MAIN DISTRIBUTING BOARD. springs were known to telegraphists as who started telephone exchanges, like all otherfounders of new industries, adopted in the first instancethat which already existed, so far as it was within theirknowledge, available for their purpose. All the firsttelephone switchboards have been traced by competenthands to a telegraphic origin. Hence the origin of the tele-phone switchboard is the telegraph switchboard, with theaddition of indicators already in use for signaling purposes. It will be remembered that telephone exchange businesswas started almost simultaneously in London by two differ-ent organizations—the Bell and the Edison companies. TheEdison company had an experimental exchange at 6 Lom-bard street. It was publicly opened on September 4, 1S79,with 10 subscribers connected. The switchboard then usedformed the subject o
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