1. A peak-discharge-output type controlling device which delivers intermittent current of a value not in excess of four milliampere-seconds for a maximum “on” period of two-tenths second and a minimum “off” period of three-quarters second. The mean value of the peak output from such device shall progressively decrease from four milliampere-seconds at maximum “on” periods of both two-tenths and one-tenth second to three and two-tenths milliampere-seconds at six-hundredths second, one and nine-tenths milliampere-seconds at three-hundredths second, and consequently to shorter “on” periods as output current increases.

2. A sinusoidal-output type controlling device which delivers an intermittent current of a value not in excess of five milliamperes for a maximum “on” period of two-tenths second and a minimum “off” period of nine-tenths second. The effective value of the output from such device may increase as the “on” period decreases, increasing from forty milliamperes for one-tenth second to fifty-seven milliamperes for five-hundredths second, and sixty-five milliamperes for twenty-seven thousandths second.

3. Any other type of controlling device which delivers a maximum intermittent current output of a value not in excess of four milliampere-seconds for a maximum “on” period of two-tenths second and a minimum “off” period of nine-tenths second.