Electronic valves.

To anyone old enough to remember the likes of radios, televisions, and amplifiers using these pre-transistor devices, the one on the right would be considered as large. So the one on the left is *expletive* massive. Not the kind of thing the average person would come across. The "crowfoot" on it gives a big clue to its source (i.e. ex-military), and it was probably used in either telecommunications - for a large radio mast - or RADAR.

Valves are still used today. Various music "enthusiasts" swear by them... just like some mad photographers even still use film (I've taken a couple of Blips of these this week for the other, er, Film journal). Various bits of sophisticated medical equipment use them too. They can be simpler than the equivalent pile of semiconductor electronics required to replace them. Downsides include their: size; high voltages required; high power consumption; and associated with that, they give off a lot of heat. Some have to be water-cooled. The general Public are less likely to come across them these days. A bunch of this year's NC Electrical Students just finished making a guitar valve amp project. When connected to a large speaker, it did sound great. Looked pretty cool too.

No doubt there are much bigger ones still, out there somewhere.

Gave the Blood Donor session a miss, as not feeling too great, and best not risk giving some poorly soul another lurgy.