Network card with relay in case of power failure

[Dovid Bender <dovid () telecurve com>]

Hi,

I am sorry if this is off topic.I was once demoed a network device that had
two interfaces. The traffic would go through the device. If there was a
power cut or some other malfunction there would be a relay that would
physically bridge the two network interfaces so the traffic would flow as
if it was just a network cable. Is anyone aware of such a network card or
device?

TIA.