Connections are shown ([Fig. 41]) for a complete sending and receiving station on this plan with a syntonic radiator and resonator indicated (though not to scale). But with syntonic resonators the revolving commutator method is not found to be necessary; the sending and receiving switch, together with the closed box for protecting the coherer in an instantly accessible manner is therefore the chief feature of this diagram.
Fig. 40
(Fig. 6 of Specification 29,069/97).—Switch at a Sending and Receiving Station, to change all the connections with a protected Coherer from receiving to sending by depressing the knob l.
Fig. 41
(Fig. 7 of Specification 29,069/97).—Diagram of connections at a protected Coherer Station with Syntonic Radiator and Collector.
Earlier Telegraphic Advances.
In April, 1895, a communication was made to the Russian Physical Society by Prof. A. Popoff, of the Torpedo School, Cronstadt, Russia, and appears in the Journal of that Society for January, 1896. In this communication the use of an elevated wire and of a tapper-back worked through a relay by the coherer current are clearly described, and signalling was effected for a distance of 5 kilometres (3½ miles).
An extract from this communication is given in The Electrician for December, 1897, Vol. XL., page 235, and from it we reproduce [Fig. 42], illustrating the tapping back arrangement.