The ECH3 is a triode hexode mixer for broadcast receiver use. The base is the continental side contact type. The oscillator triode has to supply 11 Volts peak to peak for the hexode mixer for correct operation.

A year later in 1940 the ECH3 was also available with the IO base and called the ECH33.

The classic envelope is 35 mm in diameter and, excluding the Ct8 base pins, is 88 mm tall.

References: Datasheet, ¹⁰⁴⁰ & ¹⁰⁴³. Type ECH3 was first introduced^¶ in 1939.

 
Pin Connections

Ct8	1	2	3	4	5	6	7	8
	h	m	a	g2,g4	g1(t),g3	a(t)	k	h

 
Absolute Maximum Operating Conditions^¶

Hexode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	6.3	0.2	250	100	-2	3.0	3.0	1.3M	0.65

Triode	Va	Vg	mAa
	150	-	3.3

Thanks to Frank Philipse for supplying the above PDF datasheet