These are old batteries that fed the 1AESS switch, before the cutover on 21 November 1998. The grey fluid inside is sulphuric acid.

Each battery provides 2 volts, and is warranted by the manufacturer for 75 years. It takes 24 of them, then, to provide the nominal -48 VDC that powers the equipment in this facility.

My father has mentioned that the telephone industry standardized on 48 volts, because to use 50 volts would require them to follow a completely different set of electrical safety requirements, because of the categorization.

Note that this picture and the next several pictures are from the basement of the CO, hence the unpainted concrete blocks.

Last update: Sun Jan 10 14:01:40 EST 1999, by mark@vielle