Real Metropolis Stuff

British Thomson-Houston Glass Bulb mercury arc rectifiers, advert 1939
Dudley Hill trolleybus sub-station, Bradford, England

mikeyashworth writes on his Flickr page:

"A fine representation of one of the wonders of electrical engineering - over the years with London Transport I've been privileged to see a few of these 'sci-fi' beasts (and indeed move one). They are wonderful in action - real 'Metropolis' stuff - and I recall, I'm sure, that the old Birmingham Museum of Science & Industry (that joyful old place on Newhall St that we visited so often in the 1960s to press buttons and watch things work) had one that worked.
BT-H, part of AEI, were based at Rugby and were one of the great names in British electrical engineering. The advert notes that this was built for one of the trolleybus sub-stations, Dudley Hill, on the Bradford, Yorkshire, network - the system destined to be the last UK trolleybus operator until 1972".