This is a monument to electronic vacuum tube technology. On top is a transmitting tube of 1930's vintage, typically used in AM broadcast transmitters. It is a directly-heated triode, I'm not sure of the exact type number. The receiving tubes in the bottom are all 'TV junk': types for which there is no-to-little demand today. To be honest, the base is not actually completely filled with tubes, there is an empty shaft running up the middle.

The transmitting tube has a partially-broken filament, probably why it was originally taken out of service. Fortunately, segments of the filament are in parallel, and there are enough segments remaining intact to make it worthwhile to light it up. That warm glow reflecting off the wood is from the filament. There is a transformer in the bottom of the internal shaft to power the filament, along with a variac (accessible at the rear) so the glow can be adjusted.

The monument is constructed entirely from scrap and surplus materials. The plexiglass base was originally a ticket or entry-form drop box. The wood pieces were cut down from a 1950's mahogany Hi-Fi cabinet.

The monument also presents a representation of the principle of broadcasting: one transmitter, many receivers. That's not really a serendipitous accident though, millions of receiving tubes were produced for every transmitting tube, so when it comes to scrap and surplus they're going to show up in according proportion.