What are these things?

[Thirteen]

http://cgi.ebay.com.au/5x-1U-48VDC-Diod ... 7C294%3A50

[Chinagraf]

Perhaps they are from old telephone systems? Possibly used to combine redundant -48 Vdc power to create isolated power rails for the system's circuits using a diode ring? I don't know what any of this means, I googled it. :) (although I get the concept) Apparently some phone systems have used this type for years because it is cheap and reliable.

[Milo]

I've got one of these things, and, yep, its a telephone unit. Mine also has + /- 15v and 20v out, which I use for power rails on some rack equipment, and I use the 48 volts for remote phantom sometimes. If I remember correctly, it can provide about 2 amps of pp: ridiculous overkill, but, hey - I got the thing for free, and its extremely well-made.

[rick]

these are a standard ABC commissioned power supplies , some are dual and triple voltages some just 48 volts .
i have a couple and run my phantom

i dont think they are for telephones i most see them in ob applications , or in the broadcast racks/distubution rooms , but at auction they run $20-50 dollars.

[Alastair Reynolds]

Probably more likely Telco based supplies,
almost anything for Telephony runs on -48V , also Microwave links, ISDN Primary rate Multiplexers, analogue Telstra Line eq/Amps, PABX, you name it. Easy to put 4 x 12V Batteries in series for mains failure . ABC would have had these for running line amps to TX sites etc. All our sites were full of them. Interestingly June 30th signaled the cutoff off Telstra's Analog Audio Network (Broadcast lines etc), no more installations and at the end of November , all analog Audio services will be completely withdrawn. The end of an era -- Guess it's all digital now for Interstate hauls