[Asterisk-Users] Hardware PSTN Gateways?

[tomoki taniguchi]

  I am thinking about setting up an asterisk PBX system for my
company.   But since I can't be at all the locations all the time I am
setting up an automatic backup system where if the backup detects that
the primay is down it takes over the IP so calls  can be made once
more.  For this reason I want to setup a seperate HARDWARE  PSTN
Gateway.
  Are there any equiptment that can be plugged into the network,
connected to a PSTN
line and just act as PSTN gateway.  It needs to handle both incoming
and outgoing calls.  And preferably handle more than one pstn line per
box.

TIA,
Tomoki