Tube-number record
ER 21 A
0 archive entries
ER 21 A is a tube type in the TubeDatabase archive (class: Cold Cathode Triode). Recorded specifications: brand Elesta, construction Triode, socket Miniature 7-pin (B7G), and maximum plate voltage 240 V. The archive does not yet hold a photographed example of this type.
BrandElesta
ClassCold Cathode Triode
BaseMiniature 7-pin (B7G)
Construction
Primary TypeTriode
EnvelopeGlass
SectionsSingle
Filament / Heater
Absolute Maximum Ratings
Plate Voltage240 V
Cathode Current25 mA
Typical Operation
| Mode | Plate V | Gm (µmhos) | Rp (Ω) | µ | Plate mA |
|---|---|---|---|---|---|
| Relay Operation | 220 V | — | — | — | 22.5 mA |
Application Notes
Used in relay amplifiers, photo-contacts, light barriers, and electronic timers. Requires an RC snubber or short-circuit winding for relay drop-out delay to prevent chattering.
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