Early SCADA from ENR - May, 1917

Distant Stage Recorder Adapted to Telephone

The utility of the Stevens distant water-stage recorder has been increased by making it work over a telephone line without interrupting communication. The old machine required two circuits and three special wires, over with impulses were sent in response to the movement of the stage-measuring float. A receiver and recorder were mounted on one bedplate, and in place of the float Pulley on the shaft of the spine wheel which drove the pencil carriage, there were fixed two ratchet wheels with opposed teeth. Playing over these ratchets were pawls carried by loose arms on the spine-wheel shaft. One of the other of these arms was pulled down by a solenoid wherever the proper circuit was closed by the sender. The ratchet wheels were moved each time a distance proportional to one stage interval, and the pencil carriage moved to the right or left to record the change in water level.

On the new machine the sender remains the same, except that it sends the current in one direction for a rising stage and in the reverse direction for falling stage. The sending ends of the telephone circuit are joined by a repeating coil through which the sender connection is made, so that the disturbance is balanced and no effect produced on the telephone. At the distant end, a polarized relay is connected to a repeating coil. This sends current from a station battery to one of another of a pair of solenoids on the receiver and works the ratchets as already noted in the older machine. This apparatus was designed by J. F. Stevens, consulting engineer, Portland, Ore. And is made by Leupold, Voelpel & Co., of Portland, Ore.