x
exhibited to the person sending as well as to the person receiving the communication. This improvement was effected by placing a system of keys permanently at each extreme end of the metallic circuit, and by providing each circuit with a cross piece of metal for completing the continuity of the wires when signals were being received from the opposite terminus. The two signal apparatuses being thus thrown into the course of the metallic circuit, every signal was given at both ends concurrently; and the cross piece was made to restore the circuit for a reply on the first communication being completed. This united and reciprocal property is the basis of the electric telegraph, and is inseparable from the practical system. It has been my leading principle throughout, and has impressed itself even upon the forms of my instruments; their distinguishing characteristic from first to last being that my keys and signals have always been joined together into one instrument, and the several instruments into one reciprocal system. In a word, the arbitrators will here recognize the earliest form of the reciprocal communicator, the fundamental condition of the electric telegraph under every varied mode of its operation.
“My earliest apparatus thus comprised, in a complete though improvable form, two essential parts of my system of a practical electric telegraph, viz., the detector and the reciprocal communicator: a third of equal importance is the alarum, without which the electric telegraph would require to be constantly watched, like ordinary telegraphs.
