Erich Zepler had married Eleonore Fischer in 1926. In December 1935 he left Germany because of the rising intensity of racial persecution by the Nazi government, and moved to England. His wife and children followed soon afterwards. Unfortunately his parents were not allowed to move to England, and his father died in 1939. Tragically, his mother became a victim of the Holocaust in 1943. In England he anglicised his name to Eric Ernest Zepler, and his wife and children were called Lore, Carole and Matthew. His family would become naturalised British subjects in 1947.

Before leaving Germany, Zepler arranged to join the Marconi Wireless Telegraph Company in Chelmsford, where he resumed his design work on radio receivers and transmitters, and worked hard to master the English language. He became responsible for the design of the Marconi CR100 superhet receiver, which would become the standard MF/HF receiver on Royal Navy ships during the Second World War. It used 11 thermionic valves altogether, including 2 RF and 3 IF stages. Crystal filters were coming into use, for example in the B28/CR100 receiver. This was made in 1939, and operates over the frequency range 60 kHz – 30 MHz in 6 bands. The upper tuning dial gives a linear reading of frequency, and rotates when the band switch is operated.

The Marconi superhet transmitter-receivers 1154 and 1155, which were widely used in RAF aircraft during the war, were also based on Eric Zepler’s designs. They operated from 75 kHz to 20 MHz in 5 bands, and had direction finding and homing functions.