Before revision: The reflex principle was used in compact Australian superheterodyne radio receivers from the 1930s to the early 1950s; the intermediate frequency amplifier stage was also the first audio frequency stage using a reflex arrangement.
After revision: The reflex principle was used in compact superheterodyne radio receivers from the 1930s to the early 1950s; the intermediate frequency amplifier stage was also the first audio frequency stage using a reflex arrangement.