The Navy's high-power station, NAA in Arlington, Virginia, had begun operation a couple years earlier, and was best known for broadcasting daily time signals. Because the station was not capable of transmitting full audio, the correct time was signaled by a series of preliminary dots, followed by a dash at the top of the hour. Based on the description, this receiver used a simple regenerative circuit -- called an "ultra audion" in DeForest parlance -- permanently tuned to NAA's operating wavelength of 2,500 meters (120 kilohertz). (The plate on the front of the receiver in part reads: DE FOREST AUDION TIME RECEIVER. SET FOR U.S. TIME SIGNALS FROM ARLINGTON, VA.)
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Electrical World, March 27, 1915, pages 818-819:
Device for Receiving Wireless Time Signals
An "audion" time receiver has recently been placed on the market by the De Forest Radio Telephone & Telegraph Company, 101 Park Avenue, New York, for receiving the government signals, which are sent out twice a day, according to the explanation accompanying the diagrams shown in Fig. 2. The time signals are transmitted as shown in the diagram, being merely a series of dots one second apart for five minutes before 12 noon and before 10 p. m., ceasing on the twenty-ninth second of every minute and for the last five seconds on each of the first four minutes. They cease for the ten seconds, at the end of the last minute, and a long dash is transmitted exactly on the hour, the time being taken at the beginning of the dash.
Besides the necessary tuning apparatus, an "audion" detector is inclosed in a waxed piano-finished oak case, 13 in. long, 11 in. wide and 11 in. high. All metal parts are heavily nickel-plated, and all switch and control knobs and binding posts are of hard rubber. The front panel is of black composition material. According to the manufacturers, when once the set is adjusted it will remain so from one end of the year to the other. When one is through using the set, the head receivers are hung on the hook at the left, so that their weight pulls it down and automatically shuts off all circuits.
The wires running to the aerial through the lighting switch are connected to the binding post on the set marked A. The ground wire is connected to the binding post E. A 6-volt battery is connected to the binding posts marked AA, and the tips of the head set to the binding posts marked TEL. The wire leading out from the grid in the bulb is connected to the binding post G and the wire from the wing in the bulb to the binding post R.
At five minutes before the hours on which the time signals are sent, Eastern time, the head set is lifted off the hook and the bulb is immediately lighted. The rheostat knob under the lamp socket is turned away from "in" toward "out," until the filament of the bulb becomes normally bright. The switch B is started at the lowest point No. 12, and is turned to the right until a blue discharge occurs in the bulb or a hissing noise occurs in the receivers. The switch is then brought back one point at once, as the blue discharge, if prolonged, is detrimental to the bulb. The knob PC is now moved from the lowest left-hand contact point around the arc, and at the same time, the knob LC is moved slowly until the high-pitched time signals come in loudest. When this occurs the set is in "tune" with the government station. If other signals interfere with the time signals, the knob LC or VC is turned to the left to reduce the interfering signals. The switch knob PC is also adjusted slightly.