The 6688 is a special quality UHF high-slope RF pentode primarily intended for use in wideband amplifiers in telephone carrier systems, radar equipment and measuring equipment.
The Type is etched into the glass as well as being printed. The GE logo covers the end etched letter of USA.
The pentode is a small part of the miniature envelope.
The thin glass tube envelope is 21 mm in diameter and, excluding the B9A base pins, is 37 mm tall.
