What is a Transcription Turntable

My Linn LP12 is labled a trascription turntable. What does this mean in audio terms VS. a regular turntable?
The term has been co-opted over the years to mean simply "high fidelity", but originally it was a turntable that could play 16-inch transcription discs common from about the mid-1930s to the late-1940s for radio station use. These 16-inch transcription discs were cut at 33 1/3 rpm and could hold about 15 minutes of continuous playing time per side (as contrasted with 5-7 minutes for 78s regularly played in that period) and were often used for syndicated programs or government broadcasts. Most radio stations had equipment on which they could cut their own transcription discs of programs or for spot commericials. Some transcription systems encoded the signal in a side-to-side playing groove, but at least one used vertical grooves requiring a separate tonearm/cartridge. Thus, the tables often accommodated two arms.
Wow, Rushton. Excellent post--thanks for the info.
Thanks Rushton that is an excellent piece of history. Much appreciated
Glad it was helpful - my father did work for radio stations for many years, and I remember seeing these big rigs when I got to travel with him (all sitting idle by that time in the early 1960s). Here's a picture of an old RCA transcription turntable:

Rushton...Good info. Some audiophiles used to use transcription tables, and one reason was the longer arm which supposedly made for better tracking. At 33 rpm I would have expected a 16 inch disc to give play time longer than 15 minutes. Also, I think that large format discs were also made at 16 rpm for even longer play time.
Just going from recollection on the playing time, Eldartford. Longer may well be true, and my recollection may be for 16" 78s. The speed issue was also all over the map from 16 rpm to 90 rpm, and playback allowed for all of that variance. Interestingly to me, KAB still manufactures a "transcription" turntable that will manage those 16" discs and allow for infinitely adjustable speed control throughout this range.
Great post Rushton. I beleve that Simon Yorke built a few transcription turntables for the Library Of Congress in the last couple of years. Nice rigs!
Looking for help to identify what was likely a very high end "transcription turntable" in its day. Tonearm has "PC" in a circle logo. I can send photos if anyone cares to respond to this. Thanks!!
The disks are impressive to see. There was one in a junk shop that just seemed huge when you held it in up ... with RCA and filligree on one side and grooves on the other. In red vinyl.

I really should have bought the thing!