This standard (Part II ) covers letter symbols for use in the field of diodes, such as rectifier diodes, low power signal diodes, tunnel diodes, voltage reference and voltage regulator diodes, variable capacitance (varactor) diodes, and microwave diodes.
IS 3715 Pt.2-1971 history
1972IS 3715 Pt.2-1971 Alphabetical symbols for semiconductor devices Part Ⅱ Diodes