1. The output voltage is determined by the Zener diode (VR voltage and the voltage drops across the optocoupler (U LED and resistor R

2. Other modifications were Amal alloy (aluminium) control levers with click-stop cable adjusters, production of which BSA took over from Amal, marketed under their 'Motoplas' accessories branding, and the Zener diode voltage regulator was installed in an aluminium heat-sink mounted high on the front frame tubes to benefit from the cooling airstream.