The 4687A is a voltage stabiliser tube. The 4687 is on a Ct8 base and this variant has the B4 base. Both have identical electrical characteristics.
The striking voltage is 130 Volts and the regulation is 6 volts across the full current range. The working gas is neon.
The wide glass tube envelope is 25 mm in diameter and, excluding the B4 base pins, is 86 mm tall.
References: Data-sheet & 1040. Type 4687A was first introduced in 1937.
Absolute Maximum Operating Conditions¶
Updated February 23, 2013.