Radio beacon and to synchronize the sending intervals of several stations in a group so that they will not overlap

The actual work of synchronizing is accomplished through control of the "on" and "off" periods of the transmitter by accurate clocks. Two types of clocks are used to accomplish this, the larger number being of the marine escapement type which are serviceable alike at ship and shore stations. Pendulum clocks are also used at a considerable number of land stations. Both types of control clocks are equipped to close an electric contact at the beginning of each minute. This contact is in series with the windings of an electric solenoid or a similar device, which when the contact is closed advances the drum, carrying the other and larger electrical contacts one step at a time.

This multicontact drum, called a synchronizer or secondary clock, is also divided into minutes, or spaces corresponding to minutes, and makes one complete revolution in an hour. It is this drum that provides that the radio beacon signal shall be emitted for exactly one minute and be silent for two minutes. It is also feasible to select any other "on" and "off" arrangement so long as the changes occur at even-minute intervals. Incidentally, this multi-contact drum which is advanced at minute intervals by an accurate clock, provides a ready means of closing and opening other circuits in addition to those controlling the "on" and "off" minute periods, thus furnishing the means by which any radio beacon station can be made fully automatic.

For example, one contact can start a gasoline driven electric generator, another contact can place the transmitter in operation, while another controls the duration of the characteristic signal period, the operation for 15 minutes in each hour.

Although the control clocks are accurate and sturdy, it is necessary to provide for correction and adjustment against a standard time signal. An attempt to permanently fix the electrical contacting mechanism to the clock time train and depend on regulating the clock to correct for accumulated errors, was found to require too frequent adjustment of the clock.

Instead of this, the contactor itself in the clock is made adjustable, so that the instant of contact can be advanced or retarded manually as necessary to allow for accumulated clock' error. This adjustment is made by a suitable device without opening the clock. This provides a ready means whereby the attendant at the radio beacon station can listen in on the other radio beacon stations in the synchronized group and correct at once for any errors. This is done twice a day. For this purpose one station in each group is taken as a master station, to which the clocks at the other stations are adjusted. The clock at the master station is adjusted twice a month from the standard time signals.

Warning Device.—Automatic operation of radio beacons is at present being provided in many locations.

In order to insure operation without the constant attendance of the keeper, a positive warning device has been developed whose function it is to notify the keeper in case of failure of any part of the radio-beacon system.

The function of the radio-beacon transmitter system is to induce an r.f. current in the antenna, and the warning device being actuated by the antenna current, automatically sounds a warning, in case the antenna current for some reason is being interrupted.

The device operated by sounding a gong or horn whenever the aforementioned antenna current (radio signals) stops for a longer period than two minutes, this being the normal silent period.

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CHAPTER 26

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