I wrote this article about a month ago but with a fairly mental workload at My Real Job, it kind of got put on the back burner.
My interest in the C470 IP was originally peaked when I asked on Whirlpool about some handset suggestions last year when I wasn't satisfied with the Telstra E5100 handsets I was using with my Billion 7404VGP. The original problem was that my E5100's wouldn't audibly 'ring' when a call came in over the VOIP line - they'd display the calling party's number, but not audibly ring. This gave me a good excuse to change to an all digital setup anyway - I didn't like the unnecessary conversion to analogue and back again. When Decryption mentioned a month or so ago he'd been given one as a review unit - I jumped at the chance to get my hands on one.
VOIP Basics
I guess a bit of background is required on VOIP setups and how they work. First of all your digital handset records and encodes your voice as a digital stream, then it sends it as a digital stream to the base station. So so far we've got Voice -> DECT handset -> base station.
The next step differs on your setup. If you have a standard PSTN (Public Switched Telephone Network) service, at this point your call is converted to analogue and enters the network to be switched about and bastardised by Telstra. If you've got a modem/router that does PSTN and VOIP switching or Least Cost Routing, you can plug a device like Billion's 7404 series into a land line and also set up a VOIP service on it. From there by setting up detailed dial plans your calls can be routed on the fly to go over the appropriate service. Local or interstate call? Route it over the VOIP service. Location dependent or free call (such as 000, 13 numbers or 1800 numbers)? route it over the PSTN.
This worked great but because the handsets I were using were designed for the PSTN there was this extra level of digital->analogue->digital conversion happening most of the time when I made VOIP calls, which were 99.99% of the calls I made. So the path of my voice would be something like:
- My voice travels as an analogue sound wave to the DECT handset
- DECT handset then essentially records this and sends it digitally to the basestation
- Base station sends an analogue signal to the modem/router/SIP device (because it's designed for the PSTN)
- Modem sends a digital signal over the internet to your VOIP provider.
- Your VOIP provider then converts this signal back to an analogue signal so it can travel over the PSTN to whoever it is that you're calling.
So, in the above scenario the signal would be Analogue, Digital, Analogue, Digital, Analogue.
Obviously the first Analogue component we can't change until we can plug a phone into our brain or something and the last part is dependant on who it is you're calling. Unless you're calling another VOIP user, the chances
...