Payback time on solar panels just takes to long. Their are eu countries that subsidise buying panels for your house.

That said come campers or vactionhouses have solar power because there is no electicity. But if there is electicity it's cheaper that buying solar power. And you can always go for green energy in many countries.

Found a nice very small pbx that needs very little ram and can run from small dedicated machines.

Just don't know if it supports callback, it says to have all asterik plugins.

Askozia Embedded PBX Solutions - AskoziaPBX

You can download and burn a cd and install it.

Yes, this is completely true for big domestic systems that feed into the grid. However, a small server based on laptop technology (and ideally running a solid state hard disk) would only need a 15W solar cell which can be bought for around 60 Euros. Maybe I should just build my own at some point! :) e.g. Based on an inexpensive netbook with a decent battery.

Thanks also for the link for the Askozia pbx. I will try and investigate that this weekend.

By the way, I found some old PC based software which seems to configure a bridge between 2 SIP calls on a PC running back at your home. It is meant for bridging an incoming call on one DID to an outbound SIP call (any provider), but it can also be configured for callback. From the user guide, it seems to be very easy to use and set up. I know this can all be done if you are Asterisk savvy but for an amateur like me this seems pretty perfect. Unfortunately, the software costs $29. However there is a 15 day evaluation period. I have not tried it yet, as I may save my evaluation period so that it occurs during my holiday when I will need to make use of the callback. Knowing my luck, the evaluation version will not allow callback.

The software is called dialbridge and it can be found here:
VONaLink - DialBridge for Windows

Info on the callback method can be read here:
VONaLink DialBridge for Windows User Guide

Many years ago I did have a windows based callback server. Only problem was that it only worked thru analog or isdn lines. I had a isdn card in my server, called my isdn number go busy tone and the software would call me back thru the isdn line. I would than get a dialtone and would call out on the second isdn channel.

This was still in the days that lichtenstein numbers were cheap to call.

I tried at that point to get if working thru voip and could only do that by hooking up the isdn card to a fritzbox voip modem. So yes you can do it but you need a good isdn card and it might be easier setting up a small asterisk based sever.

So far I did not find any dedicated windows based callback software that works with voip. asterrisk for windows does not support it, axon antoher windows based pbx does not support callback, 3cx also windows based no callback.

Your link looks nice but as far as I can see there is only 1 voip provider you can use. So that voip provider must supply you the incomming did number and you also have to use it for outgoing calls. This makes you depend on 1 voip provider. But maybe you can use a betamax brand that still has an incoming number with the account, than it might work.

Other thing I don't know if you can add more than 1 callback number if not you would have to use the did number only for callback.

But the provider that you intend to use for outgoing calls doesn't necessarily have to also supply the DID. Don't most 3rd party DID providers allow you to forward the DID to any SIP address? In that case just forward it to the same SIP address of the provider you intend to use for outbound calls. (e.g. one of the Betamax brands). This way you can use the software with just one SIP account.

Yes did not think of that but you could use it like that. Forward your did number to the betamax sip address would indeed limit you to only using 1 provider. Test it and see if it works.

I will and let you know how it works.