Electron Tubes
- See Mullard–Philips tube designation for details. A brief summary of just the more common letters is:
ECC81 / \ \\__ last digits give serial number / \ \__ first digit(s) indicate base (3=octal, 8 or 18 or 80=Noval (B9A), 9=7-pin(B7G). / \___ one letter per valve in the tube:
D=0.5-1.5v A=single-diode (low power)
E=6.3v* B=double-diode (usually shared cathode, but not always)
P=300mA C=triode
U=100mA F=pentode (low power) L=pentode (high power) Y=Single-phase rectifier Z=Full-wave rectifier
* Note: some 6.3 Volt heater types have a split heater allowing series (12.6Volt; the default for Noval pins 4 to 5) or parallel (6.3Volt) operation.