SPA-2100

Sipura SPA-2100 hardware SIP adapter

I (voip247) think that the Sipura SPA-2100 (80 USD) is by far the best hardware SIP adapter as of January 2006 because it totally eliminates the NAT and QoS problems that plague other SIP adapters that don't have built-in routers (like the Sipura 1000/2000/3000 and Linksys PAP2).

Note (from DracoFelis? on 5/6/2006):
Now that the SPA-3102 is out, it might be a better choice for a lot of people than the SPA-2100. Like the 2100 the 3102 has a built in router + builtin QoS. But the 3102 also has the 3000's ability to cross-link with a real "phone line" (allowing your to use your normal phone line and VoIP from the same "phone"). And the 3102 also has the 3000's ability to use multiple outbound providers from the same "phone".

At this point, the 2100 has only these two advantages over the newer 3102:
1) The 2100 is a few dollars cheaper.
2) The 2100 allows two phones at once (since it has two phone ports).

But OTOH the SPA-3102 has all these benefits over the 2100:
1) Newer design (which hopefully means it will be supported longer).
2) Ability to fully access/use/control a real phone line (or anything that mimics a phone line, including another VoIP adapter), in addition to VoIP, from the adapter. This also means you can do things like route some calls (911, local calls, toll free calls, etc) via your existing telco line (if you still have one) while still using VoIP for cheap calls elsewhere (all from the "phone" attached to the adapter).
3) Builtin support for multiple (outbound) VoIP accounts, whereas the 2100 only allows one VoIP provider/account per phone jack.

NOTE: In other ways, the SPA-3102 and the SPA-2100 (below) benefits are pretty equal.

SPA-2100 features and benefits

• The SPA-2100 eliminates the NAT problem by being both a router and a SIP adapter, which allows it to use your public IP address in SIP messages. The most common NAT problem is one-way audio (the other person can hear you, but you can't hear him). If your SPA-2100 is plugged directly into your DSL/cable modem and you have one public IP address (which is typical), then your SPA-2100 will use the public IP address (rather than