The Universal triode from Myers is of double ended construction to reduce inter-electrode capacitances and was a successful product. It was also known as the RAC-3 and is a bright emitter. It was later superseded by the dull emitter Dry Battery valve.
Initial introduction was in Canada in 1922. However Myers had worked with De Forest, RCA etc. in the USA making valves and infringing patents along the way. Technically a good valve, the company moved back to the USA after the expiration of the De Forest patents but legal action by RCA for back royalties drove the company to bankruptcy.
The attached .PDF file is a reproduction of a 1924 article from Wireless World.
The glass tube has the etched words Made in Canada.
The central evacuation pip and glass beads holding the electrodes rigid.
The black end has the control grid and f(-) connections. The box gives details.
The red end has the anode and f(+) connections.
The anode with helical grid within. The filament is secured in a fold in the support. The other connection is to the grid.
The other end also has connections to both the grid and filament from the glass bead. Thus all three electrodes are supported at both ends.
The thin glass tube envelope is 16 mm in diameter, and including the base pins is 85 mm tall.
References: Data-sheet, 1047 & 3002. Type Universal was first introduced in 1922. See also1922 adverts.
