A Wireless Alarm

Radio Record, Volume III, Issue 22, 13 December 1929, Page 12

A Wireless Alarm

For Uvtannounced Broadcasts, . ; D*. RISTOW, the German scientist who invented distance-control for receiving sets, has recently patented a device by means of which a transmitting station may call listeners when their receiving sets.are not actually in use, The device, the effect of which is similar to a call to a subscriber from his telephone exchange, can’ be employed for individual receiving sets and selected transmissions or adapted for general use by broadcasting listeners. . Although, by reason of its cost, the apparatus is not thought likely to be of immediate use in broadcasting, it is possible that a simplification may later on render it of use for this purpose also. The calling is done by Morse signals, the receiving set being adjusted to respond to particular combinations of dots,and dashes. The. response to the call -is dependent upon a calculated rhythm in the Morse signals, To obtain this rhythm a special Morse apparatus, also designed by Dr. Ristow, is used at the transmitting end. The call is made at the receiving end by an alarm bell (the device is ‘called the Yunkwecker-wireless alarm), but any other means, such as a lamp, could be employed. As in the case of the distantly controlled receiving set (which enabled the Police Presidency in Berlin to overcome the difficulty of local disturbances), Dr, Ristow’s invention wis made primarily for official purposes. The advantages of being able to call up any particular receiving station--and the German police have many dozens of receiving stations throughout the country-immediately before the transmission of an official message, are obvious. ‘The system would also be of use, it is thought, to the lire brigade, who are to be supplied with