[c-nsp] 12V DC input on 2950

[Bill Wichers]

> We're trying to mount a 2950 in a vehicle as a mobile lab for testing our
> wireless network.
>
> There is a 12VDC marking on the back of the chassis next to a plug, which
> I understand is for the Cisco RPS chassis to connect in.
>
> We've found the pinout for the connector, and it mentions -48VDC on some
> pins and 12VDC on others.
> Does anyone know if the -48 is required? Or can we just feed it 12VDC on
> the pins marked for it?

It probably needs both voltages. Trying to run it with only one of the two
voltages might damage it. The easiest thing to do would be to get a small
inverter and use that to convert your vehicle's 12v DC into 120v AC to run
the switch "normally". I don't have a 2950 handy to look at, but I don't
think you'd need more than maybe 200 watts or so to run it. That's a bit
much for a lighter plug, so you'd be best advised to wire the inverter
directly to the battery in the vehicle.

You could also string four 12v batteries in series to run a -48vDC version
of the 2950, but that would limit your runtime if you don't have a way to
charge the batteries (which would require about 54-55 volts DC).

     -Bill


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Waveform Technology
UNIX Systems Administrator