Mystery Radio

Lost in the scramble of early radio design were a number of circuits whose sole purpose was to decrease the quantity of tubes necessary for adequate reception and reproduction.  The Reflex circuit and its sibling Inverse Duplex enjoyed wide popularity.  A few companies, like ERLA, David Grimes, and Acme Apparatus, were built upon the hope that these patents would carry them to long-term viability. 

The chart below, from the 1931 edition of Moyer and Wostrel’s Practical Radio Construction and Repairing tells the story best.


As the cost and availability of vacuum tubes came down, the appeal of marginal, finicky circuits abated. Larger companies, like Crosley, were able to survive the passing of the Reflex circuit.  The slogan for their Trirdyn models was “Three Tubes Do the Work of Five.”   When the Reflex fad subsided, they had other patents to fall back on; ERLA wasn’t so lucky.

According to Alan Douglas in his Radio Manufacturers of the 1920’s, George Pearson decided to go into the radio business “in the fall of 1921.”  By 1924, his Electrical Research Labs, or ERLA, had ads in all the major radio magazines promoting a complete line of beautiful components, all designed to serve the hobbyist who wanted to build their own Reflex set.  Articles on the ERLA Reflex circuit were in virtually every new radio publication on the market.

		ERLA semi-fixed crystal detector