372 CURRENT TOPICS. [J. E. I.

An Electronic Relay for Initiating Vapor Discharge.-EDWARD C. DENCH. (Electrical Emgineekzg, Vol. 59, No. I I .) The recent introduction of low-voltage fluorescent lamps has created a need for automatic control auxiliaries. Several methods have been de- vised for the automatic starting and operation of these lamps, the most recent being a device known as the “glow relay.” Earlier methods had certain disadvantages as to cost, effect on the lamps, circuit efficiency, dependability, and ease of wiring: The invention of the glow relay resulted from attempts to overcome these unde- sirable features. The relay is essentially a small glow-discharge lamp, comprised of two electrodes in a glass envelope containing neon. The container is about the size of an automobile headlight lamp. One of the electrodes is constructed of a heat-sensitive bi- metallic strip with a contact member at its extremity. The other electrode is a projecting wire placed so that it will touch the contact member when the bimetallic strip flexes due to heating. When a gaseous glow discharge takes place in this device, the bimetallic strip is heated by positive-ion bombardment and flexes so that the contacts are closed. When the contacts make an electrical connec- tion, the glow discharge is short-circuited. The device is designed to have a break down voltage of about 90 to 100 volts. The glow relay has many advantages over previous fluorescent-lamp auto- matic-starting devices. In addition, it may be stated that the relay, although first developed for use with fluorescent lamps, is not limited to use’with these particular lamps. It may find application in the automatic control of other discharge devices of the same nature which exhibit the same phenomena.

R. H. 0.