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We are currently designing a family of Netonix switches more targeted towards the Telecom -48 volt environment.

Since we (ok..me really..) are not that familiar with the -48 volt telecom environment, I would like to get a some suggestions and guidance from
some of our more experienced operators.

I am looking for someone to describe their typical setup, and suggest what is needed to meet their requirements, more from an electrical point of view. For example, I know we have had a few telco guys buy our DC switches, and then have had to buy an isolated dc-dc supply to put in front of it. I (ok, me again..) want to design a version of the switch so no
extra isolation supplies are required to be used, other than the switch itself.

I am looking for someone who has a bit of time to confirm I am doing it correctly, and who would also field test new telco switches for us.

What..a company that asks the users what they need & want...how crazy is that....

Dave

Dave I'm shocked you didn't get anyone jumping on this.

Years ago I tried to integrate a tough switch with a -48 teleco power system. The biggest challenge I came up against was the radio's ground and the dc- were bonded together within some radios and passive injectors.

I remember some hardware versions of ubnt were and some were not, but it seems mikrotik's were much more unpredictable. For instance I remember installing a mikrotik ap and all was good then one night in a wind storm it shorted and killed the MT and the switch. In the end, I ended up reverting to AC and good ol tripplite interter/charger.

I quickly just metered several ubnt radios on the bench and only found one with the - input and the shield bonded. Admittedly it was marked "Dead?".

Would LOVE this.

Would also love 10Gb support.

In this situation, are the units able to provide 24V, 48V, and -48V POE? I know that the Trango is -48.

Steve

I'd agree the critical part is an isolated power system. Everything in our racks must be grounded and our return power (+48V) is grounded. However the devices that are running on +24 and +48V cause lots of issues since they usually are grounded to the negative voltage.

The other thing that I would love to see is a different power input. I wasn't sure about it when I saw it online, and now that we received our first unit I know I don't enjoy the design. The lack of isolation means we can't use it in our -48VDC systems, but the power input also means it would not be mounted into any of our telco racks. Everything should have a connector, that can be screwed down to be locked into place.

The last thing I'd love to see, is all of our -48 systems are redundant. So redundant power supplies or even at least dual power inputs would be extremely helpful. And at just the level of redundant inputs they would have to have blocking diodes. When we work on our battery plant we shut all of the A feed off or all of the B feed off at a time. We wouldn't want to have power feed back into the system.

Just the first thoughts I've had. Looking forward to playing with the switch more, I think it's going to be great at our remote residential sites.

There's a tower site we rent space at, which has a CellCo as the primary client at tower-top. Putting a (-)grounded WISP setup on the same tower as (+)ground Cell gear results in a 96v differential between our grounds, so maintaining proper isolation is a challenge. Could definitely use this switch.

Make the input an isolated dc/dc and dont bond either + / - to ground, then you do not have a specific negative or positive version. Just and a seperate grounding conductor.
Might want to have a peak at ETS EN 300 132-2 etc. Most (W)ISPs might not care too much about the noise requirements in the speech range though.
Good screw terminal connectors or similar instead of banana plugs.

PhilipO wrote:Might want to have a peak at ETS EN 300 132-2 etc. Most (W)ISPs might not care too much about the noise requirements in the speech range though.
Good screw terminal connectors or similar instead of banana plugs.

One does not have to use the Banana Plug if they are concerned about possible noise, they can unscrew the terminals and stick the bare wire through the post hole and tighten.

Not sure where you are with this, but I'd love to test it. You could also bring one to Baltimore if you wanted to take a look at a -48 setup and see how it would be deployed in the real world.

As others have said, it would just be an isolated DC-DC. I would much prefer dual hot swappable power supplies as we generally run A and B power at -48 sites.

Personally I would love to see a smaller switch like a 12 port made available too... The 24 port is just too big for some cases. I just finished a setup where we used a 12 port with a -48Vdc to +48Vdc converter to power things up... We only needed 3 or 4 ports here, so a 24 port switch would have been over kill and too much price wise vs a a 12 with converter... But now we have one more failure point in between, so now I have to keep a spare converter around...

It also sucked too because I couldn't power it up at the office till I got that converter because everything at the office was -48V as well, so I had to wait till I was in the field to configure it all...

i think a WS-26 - idc would be perfect