Sensibly equivalent¶ to:
The 5A/170K is a special quality high-slope RF beam tetrode primarily intended for use in wideband amplifiers in telephone carrier systems, radar equipment and measuring equipment. STC stands for Standard Telephones and Cables.
It can be seen that in this miniature envelope is an even smaller valve, this very small size helps to reduce inter electrode capacitances and thereby raises the maximum usable frequency that the device can operate at.
These valves would be used up to the UHF region of the spectrum. In telephone systems a single carries has a large number of separate telephone calls modulated upon it
The thin glass tube envelope is 21 mm in diameter and, excluding the B9A base pins, is 33 mm tall.
References: Datasheet & 1040.
Absolute Maximum Operating Conditions¶
Updated January 26, 2013.