davek78 wrote:I require a VOIP Gateway (if that is the one I can simply plug in to my router/ network point and does not require my computer to be on)
Let me start off by saying if you are adamant that you do not want an IP phone but prefer the use of a standard telephone such as a traditional BT corded phone or Dect phone then that limits you to an analogue telephone adaptor also known as an ATA. You simply connect it to a spare Ethernet port on your router and plug a standard telephone into the back of the ATA.
While these are very powerful devices they do have their limits. You say you would like 4 (or more) channels? Most ATA's come with only one or two phone ports, each phone port can only handle one inbound call, you then need to make use of call waiting.
You have an ATA with one phone port, you have a BT corded telephone connected to it and you receive an inbound call, you pick up the receiver and start talking when suddenly a second call comes in, no problem call waiting alerts you to the call, however a third person then calls your number this time they get sent straight to voicemail.
If you go with an ATA that has two phone ports then when you take a call on one phone and a second call comes in this will be sent to the second phone. If both phones are in use on active calls and a third call comes in call waiting will notify you of the call and all other incoming calls again go to voicemail.
An IP phone could easily handle many inbound calls with ease; my Yealink T48g for example can handle 29 simultaneous inbound calls.
davek78 wrote:I need to be able to have 2 separate lines coming in plus a Skype SIP (I think I would prefer 4 (or more) channels to 3 so I have one spare).
Some VoIP providers do have restrictions on SIP channels however Voipfone.co.uk does not, they provide you with unlimited SIP channels. You will however need two extensions , one for "line 1" and the other for "line 2". AS for Skype, Skype does not use the SIP protocol, it is a closed system and as such will not work with any SIP hardware.
davek78 wrote:I assume I would be able to set up a gateway to "divert all calls to voicemail" for one of the channels as and when required.
Yes, you could set all inbound calls to go straight to Voicemail on Line 2 while allowing all calls on Line 1 to come through.
davek78 wrote:So... I am looking for some advice on the best gateway for my needs and whether I am right in thinking that all I need to set it up is a spare ethernet port on my router and the relevant "SIP" accounts to be set up for me to program the gateway?
Simply put... Yes
The Obihai hardware allows even more control over incoming calls, they can identify a person via their caller ID and divert their call to voicemail while allowing all other calls through.