These are indeed different beasts. Around here (upstate NY) for many years they only used the CO powered version that turned a two-pair T1 into 24 local loops. A SLC is a much more sophisticated piece of equipment, originally multiplexing 96 lines onto 4 or 5 DS1s, and now handling up to 2048 lines onto various combinations of fiber and copper. SLCs are all locally powered, and if the power goes out, there better be a guy in a truck with a generator going around recharging them all several times a day.
Yeah. Verizon's FIOS in effect puts a SLC on your house, with a battery that it's your job to replace every couple of years, and when you forget and the power fails, you lose. The decreasing resiliency of the phone system to power failures is a real problem that nobody seems to be addressing.
Regards,
John Levine, snipped-for-privacy@iecc.com, Primary Perpetrator of "The Internet for Dummies", Information Superhighwayman wanna-be,