On 4/14/18 6:09 PM, Forrest Christian (List Account) wrote:
For various reasons you need positive voltage if you're doing traditional power-interruption canopy style sync.  I.E. the type of sync which the PowerInjector+Sync will do.  This general statement might not be 100% true with the 450i (and perhaps some other more recent radios), but suffice it to say that negative voltages aren't easy to deal with for sync.   Because of this requirement the PIPS requires positive power.

Makes sense. I was thinking about using some to power stuff that doesn't need sync (licensed radios) since I had them on hand instead of buying something. Does the power only SiteMonitor 4 Channel Gigabit PoE Injector & Controller will work fine with -48VDC or does its control power come over the bus connectors from the base unit? But then I think I remember a thread where the sitemonitor base unit itself only works with positive voltages.

On the rackinjector, we support the newer Cambium style sync, which doesn't much care about polarity, and also a polarity agnostic board which also doesn't care about polarity.  For this reason, you can feed negative voltages into the rackinjector.  Currently, you have to have at least one of the three power supplies feeding the rackinjector set up for positive voltage, and the other two can be positive or negative or whatever you want, depending on the requirements of the expansion cards and the radios.

No problem for me to throw a small DC-DC converter in the mix and feed it a positive voltage on one of the inputs for controls.


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