Critical Uncertainties

Back in the day the old Strowger telephone exchanges were incredibly tough electro-mechanical beasts, and great fun to play with as well. As an example of their toughness there’s the tale of how during the Chilean ‘big one’ a Strowger unit was buried in the rubble of it’s exchange building but kept happily clunking away for a couple of days until the battery wore down. Early Australian exchanges were Strowger’s, my father actually worked on them, and to power their DC lines they used to run huge battery pairs that alternated between service and charging. That built in brute strength redundancy also minimised the effect of unreliable mains power on network services, remember back in the day power wasn’t that reliable. Fast forward to 1989 when we had the Newcastle (NSW) earthquake and lo our local exchange only stayed up for a couple of hours until it’s batteries died.