A-P-Two-In-One

This tube had an unusual structure with 2 triode sections using a common 8 shaped plate. The 2 grids were connected together and the filament was center-tapped with the mid-point connected to the shell. This arrangement made it possible to run one section at a time but it was not normally used in this way. With both sections in operation the tube was similar to an '01A and the I-f was then 0.25 Amp.
The tube was designed by Henry K Huppert. He was an X-ray technician but came to work for Moorhead Laboratories in 1917. He designed this tube and the A-P Solenoid tube.

The 2 in 1 tube was patented and Huppert applied for this on 11th June 1924. Patent No 1597893A was granted on the 31st August 1926. No records have been found to indicate that Huppert assigned the patent to Moorhead Laboratories, but continued to own the patent, himself. When Atlantic Pacific Radio Supplies Co closed, Huppert was unemployed but joined the new company Atlantic Radio Laboratories when it was formed in 1924. He designed variations of the 2 in 1 tube there. The earlier version of the A-P 2in1 tube is not mentioned in the "Saga of the Vacuum Tube.

History of this tube is covered extensively in the article 'Henry K Huppert and his Tubes" etc, by Eric P Wenaas, in the Antique Wireless Association's Review, Vol. 30, 2017, pages 173-222.

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