Testing a vacuum tube (or valve in the UK) requires setting a number of parameters for that particular tube. As a result, tube testers can have very complex panels with many knobs and settings. Several tube testers, including the Soviet L1-3 and L3-3 models, used punch cards to automate the setup. The L1-3 was introduced in 1963 and the L3-3 in the 1980s .

To test a tube, a card is placed on the patch board on the machine's face. Configuration pins are pushed into the patch board through the holes in the punch card (see cryptomuseum.com).