valve, tube, thermionic, electron, triode, tetrode, pentode, power,
magic eye, tuning indicator, nixie, history, data, data sheet,
specification, amplifier, radio, octal, B9A, B7G, B4, IO, KT88, KT66,
12AX7, 12AY7, 12AT7, ECC81, ECC82, ECC83, 6L6, 6V6, EL34, EL84, EM34,
EM80, EM81, EM85,
Mullard, Cossor, GEC, Gold Lion, Marconi, Svetlana, Brimar, Ferranti,
RCA, Sylvania, GE,6202, amperex, arcturus, brimar, channelmaster,
colvern, cossor
dario, debanks, edicron, ediswan, ei, elpico, emi
emston, era, eratron, ever-ready, ferranti, ge, gec
heinz, kaufman, haltron, hivac, hrs, itt, jackson
lamba, lorenz, marconi, mazda, mullard, national, osram
philips, rank, raphone, raytheon, rca, rft, selectron
sovtek, standard, svetlana, sylvania, telefunken, tronix, tungsram
united, valvo, westinghouse, zaerix
M.E.C. TEST
Directly heated sub-miniature triode

Height overall - 64 mm (2 1/2")
Envelope diameter - 14.8 mm ( 0.58")
Base - Miniature 4 pin, pins in a square about 7.5 mm
on a side,
one larger pin, 3 mm, three pins 2.4 mm.
Not visible above and engraved above the 'M.E.C. TEST'
label, is
'H 1.5' which presumably indicates heater voltage.
I haven't attempted to measure characteristics or
determined the
pin out.