Editing Pro Electron (section)

===Differences between Pro Electron and earlier valve-naming conventions ===

* Unlike the tube naming convention, if there are two transistors in a single envelope, the type letter was never repeated - so a dual NPN RF transistor might get a type "BFM505" rather than something like "BFF505" for instance. 
* Although some of the most popular devices conform to a pattern of serial numbers that identified package type and polarity, many do not.
* The letters assigned for the second character of transistor and diode type numbers differ in several ways, e.g.
** "B" tends to be used for dual ''varicap'' diodes
** "L" in the context of transistors designates RF power (transmitting) transistors; for valves it meant a high-power pentode tube (the usual choice for power RF)
** "Z" is used for semiconductor Zener diodes instead of (full-wave) rectifier valves ([[Vacuum tube|tubes]]).