Of course, this was in contrast with the 3B20 which you powered off by
turning a knob and then holding a button down for three seconds. Yep,
phone equipment. Those who ever dealt with things like real Western
Electric 303 "broadband" modems recognized that behavior. You commanded
loopback on them the same way.
Ron, pls don't forget the best 3B20 power-up feature, the pull starter in the middle (power) cabinet. Seriously there was a cable that pulled out of the middle power box (that looked like a small engine pull starter) that used to by-pass the batteries on a true cold boot because if it was not there the battery power up would surge the incoming load and trip the mains. IIRC the off button Ron describes does not completely power it off, it just shuts it down and you can take out cards safely, but the batteries and some subsystems are still active. True 'cold' power down is extremely difficult. It is designed to stay powered.
As he said -- standard telco gear, 48V supplies, rack of truck batteries, etc.
BTW: In the same vein, I once had a movie we all called the 'burning Alpha' when the 'telco special packaged' DEC 4300 from DEC CSS went through its fire testing in NJ. All equipment that was going to be in a CO or wiring center has to be tested to see how it burns in a fire (plastic/nylon parts in a computer rack can be nasty - and there are very tight specs). As I understand the spec, all flames have to stay inside the cabinets.
One of the cute parts of the video is a sidebar, which is displaying the syslog messages during the fire. There was a desire, but I don't know if it was ever acted upon, to match the syslog messages to different activities in the fire. During the time when it is burning, there is a timer in the corner so they can note afterward at exactly which time, different things were incinerated.