 Inserting the power plug into a socket on the chassis or the side of the radio (depending on model) switched the T/O to battery operation.The first post-war T/O was the 8G005Y, designed by Robert Davol Budlong, an industrial design consultant responsible for many of the Zenith radio products.Priced at $125, it was in production from 1946 to 1949 in several variants.