Eric Zepler taught with chalk and talk, backed up by laboratory experiments. With only 18 students in the Postgraduate Diploma class in 1957-8 there was an informal interactive atmosphere in the classroom.

He welcomed questions, both trivial and challenging. In response to the latter type his eyes would narrow and his face would freeze while he contemplated possible answers; then he would respond with a diagram or some mathematics that we could all understand. We saw that good circuit design depends on an intuitive understanding of how electronic components and circuits operate. A good knowledge of circuit theory is necessary. The creative steps in a design must be followed by mathematical analysis of the proposed circuit before construction is undertaken. Remember his crucial words in 1925: “that can be calculated”.

The coverage of his course may be summarised as follows.

• Circuit theory including loop and nodal analysis. Steady state and transient responses.
• Electronic components including thermionic valves and transformers.
• Small-signal, Class A and Class B amplifier circuits. Distortion.
• Amplitude and frequency modulation. Circuits used for detection and frequency changing.
• Antennas and radio systems. Gain control.
• Shot noise, thermal noise and current noise.
• Screening and undesired feedback.

In his laboratory classes Eric Zepler would soon find out whether we knew what we were doing, by shrewd questions and gentle coaxing. Many things were difficult, and he never pretended that they were easy. He helped us to develop our insight into the operation of circuits by encouraging us to sketch currents and voltages as functions of time and frequency, and to compare measured results with theoretical predictions.