This system was originally manufactured in the1870s and is undoubtedly the first electric watch clock to be widely accepted. The
system employs a battery and one pair of wires running to all the tour stations, over which any of the stations may send a signal to this central unit. On visiting a station, the watchman wound the station mechanism's
mainspring. When he released it, an escapement allowed the mechanism to run down over eight seconds or so. In running down, a code wheel would "make and break" the electric circuit, sending a coded signal that
identified the originating station.
At the central recorder, the first signal pulse releases the recorder's clock mechanism and allows the pinion gear (seen at
the center in Fig. 2) to start "lifting" the long arm with which it meshes. The portion of that arm that extends upwards to the right carries a pinprick or a marking lead at its upper end (out of sight
here, behind a broad hammerhead). As the marking element is carried across the recording dial surface, from near the outer edge toward the center, further incoming signal pulses cause the solenoid coils to pull on the
hammer and thus force the marking element against the recording chart for an instant. This leaves a trail of dots and spaces which identifies the station.