The first all transistor hearing aids appeared in 1953. They were created to replace vacuum tubes; they were small, required less battery power and had less distortion and heat than their predecessor. The vacuum tubes were typically hot and fragile, so the transistor was the ideal replacement. The size of these transistors led to developments in miniature, carbon microphones. These microphones could be mounted on various items. There were body hearing aids where the earpiece was connected to the hearing aid and battery pack worn on the body. Ear level hearing aids consisted of eyeglass, behind the ear (BTE), in the ear (ITE), and in the canal (ITC, CIC) hearing aids.Cream plastic hearing aid with metal back. Takes 3 batteries and there is a piece of paper in the battery case advising 'CAUTION'. Two round knobs on top, 'ON/OFF' and the other I assume is Volume. There is a plastic tag for attaching to a button (probably), headphone sockets. The front is metal lacework with a scrolled 'Z'"Z" on front. "ZEPHYR/HEARING AID/2546" on back. "U C"/"M"/"7777" on inside battery case.deaf children australia, hearing aid, zephyr hearing aid