Dave,
dave powis wrote:
Phone companies work off a standard 48v (often referred to as 50v) for
exchanges and 'in building' installations. This includes mobile phone
operators. But a significant amount of equipment in the mobile network is not
in the exchange sites - it is in the BTS (Base Transmitter System) cabinets,
where 28v is used. Henace a lot of ex-mobile phone co equipment, such the
HP/Symmetricom Z380xx, Lucent RFTG's that were around, and power amplifiers
used on 23 and 13cm amateur bands, is normally capable of being powered from
either 28V or 48V supplies, since it could be deployed in either situation.
In all environments I encounter it, it is called 48V and not 50V. There
also exists a -60 VDC standard. For Europe, it is standardized as ETSI
EN 300 132-2. For US Bellcore (now Telecordia) wrote it into it's NEBS
series, but I can't recall the number from the top of my head.
The ETSI variant is online, so fetch that.
The ETSI people have created another interesting spec, the EN 300 132-3
which is for a 400 VDC system. It avoids the step of DC-AC conversion in
UPS systems since most supplies rectifies it anyway. Check it out. :)
Cheers,
Magnus
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