The golden screened HL4 triode was designed for general purpose and audio amplifier applications. It is of medium impedance and could have been employed as the first audio stage after the detector in radio receivers.

The classic envelope is 37 mm in diameter and, excluding the B5 base pins, is 87 mm tall.

Reference: ¹⁰⁴³. Type HL4 was first introduced^¶ in 1935.

 
Pin Connections

B5	1	2	3	4	5
	a	g1	h	h	k

 
Absolute Maximum Operating Conditions^¶

Triode	Vh	Ah	Va	Vg	mAa	ra	gm
	4.0	1.0	200	-3.0	4.0	11.5k	3.5