TDM400P power requirements

My current task is to install asterisk utilising a TDM400P in a Dell Poweredge 1750. This box doesn’t have the usual molex style power connectors required to plug into the TDM400P. One of the connectors on the motherboard has 12V, GND and 3.3V available which I can splice to provide the needed power.

What are the power requirements for the digium TDM400P through the power connector? Does it only require the +12V (and GND) connected, or does it also require the 5V supply?

Thanks for any help.


Not sure on the power spec, however, we have run a card in a Poweredge 750 for several months without the power plugged in (forgotten by mistake) without issue. Curious why TDM400P actually needs it?

Thanks for that. I imagine it needs the extra power to generate the ring voltage used for for outgoing calls on normal POTS phones. Maybe you’re just using your system for incoming calls? The card is recognized by the drivers without this extra power, but it does warn me that the power cable may be unplugged.

Using a voltmeter, I found there was no connection between the 5V rail on the PCI bus and the power connector, and that there is infinite impedance between the power connector’s +5V pin and any other connection I probed. I’d bet that’s a fair indication the 5V line is unused. It’s a 3.3V card anyway, so I don’t see why it would need an external +5V.

Yeah, interesting. Actually all our installs have it plugged in, except the very first (ours) where we weren’t paying attention. Interestingly, calls work fine in and out of the system. Maybe we’re just getting lucky and pushing the card in ways it shouldn’t be pushed - I’d venture!

Interesting. I’ve only done a couple of installs, but in each case I’ve had problems when I’ve forgotten to plug in the extra power.

For this system, I spliced a +12V and GND into the existing power supply wiring and plugged this into the TDM400P (no +5V). It’s all working as expected now, but maybe we should be a bit more careful next time in choosing a system which actually has the appropriate plugs for the hardware we want to run!