Why so complicated? Phone companies usually offer services where you can forward calls to another number, for example to your cell phone. You don't need any hardware for that. Or you can setup a messagebox function where you can call your home phone, enter your code, then listen to any mailbox messages.

Agree with rindi.   Clearly you can MAKE calls from your iPhone with no need to route them through your land line.

And you can simply forward your home phone # to your iPhone when you need to -- virtually all phone companies have provisions for that these days ... in most cases you can log on to a support website and do it yourself, including turning it on or off as needed.

Or you could, as rindi noted, just put an answering system on your home line and then remotely check your messages as needed.

If those won't work for you, there are several business-oriented PBX devices that will do what you want ... but they are NOT inexpensive.

The easiest solution would be to move your phone number to a VOIP provider such as RingCentral or Nextiva

At that point you can have a polycom phone at home plugged in to your router with the main number and an application on your phone which the same exact number that you could use to dial  and receive phone calls.

thanks heaps for the comments and suggestions above.

it seems i better explain the reason why i have to stick on that particular phone line: unlimited international calls offered by my land line provider. sometimes I need to stay overseas and I want to keep making international callls using the offer. that's basically where the story is from.

any more thoughts please?

hi darbid73

yes, i am in Australia, and YES it is just something I am looking for!

it seems only one thing needs to be confirm: how do i contact when i am on go, especially overseas?

do i have to call my home using mobile phone then give four-digit security code? it is okay if i am traveling in Australia as i can make unlimited national calls. but if I stay overseas, this seems not reasonable as I have to make expensive IDD calls back to Australia (which is just something I want to avoid).

or can i use an iOS app to directly connect the FRITZ box at home? that would make sense in all scenarios.  port forwarding on the internet-facing router or having VPN connection back to home will be all possible and workable for me.

is the second option possible?

thanks heaps as always.

Thanks heaps for your prompt reply.

i do have another VoIP line, which can be used to accept incoming call.

the land line to make free IDD calls is technically also VoIP based but hard coded with the provider's modem, its VoIP parameters seem not available from the provider hence using a standalone SIP phone client is no longer an option. I also notice it's MTA and CMTS are all using private IP addresses.

the 4-step process to make a call via a Fritz box let me clearly understand what kind of device it is: a relay. am I correct?

however, I guess this model should work if no extra cost for calls from my mobile phone to home (such as traveling in home country).

is there a device that can do things in a bit different way, to act as a VoIP gateway? the Internet-facing side of the device acts like a SIP server accepting my credential to sign in, while the phone side of the device acts like a relay to make or receive calls per controls from SIP client (the app running on my smartphone). am i making things complicated again? :))

thanks again.

What is the VOIP you have and what's the device?

the VoIP line is provided by an Australian provider, a pretty standard VoIP service locked to a Linksys SPA 2100 though I am also able to access the line using my iPhone with an app called Media5.

"... the VoIP line is provided by an Australian provider, a pretty standard VoIP service locked to a Linksys SPA 2100 though I am also able to access the line using my iPhone with an app called Media5. "  ==>  Does this allow you to access the line from anywhere in the world that you have a WiFi connection on your iPhone?    If so, it would seem that the Fritz Box will do exactly what you want, assuming darbid73 can confirm what I just asked about the process.

I have never tested it but I think you could have 2 free voip accounts one on your phone with e.g. Nimbuzz app. The second in your fritzbox. Your phone uses the internet to call your fritzbox then you call back out again.

BUT you need all phone accounts to be in the fritzbox which currently is not the situation.

> Does this allow you to access the line from anywhere in the world that you have a WiFi connection on your iPhone?

yes, it was tested in Asia and North America.

> The fritz box is modem, router and telephone / voip device all in one. You can even connect DECT devices to it.

it is great per the specs.

but as I already have 5 Wi-Fi routers at home, it seems not that necessary to get one more just for a phone-line-relay feature. I have also noticed its expensive price tag.

is Fritz box the only choice? no any other vendors making the same or similar things? is there a device dedicated doing this relay job?

thanks again. I really appreciate your time and effort.

thanks so much for the valuable comments and suggestions. i really appreciated your expertise, time and effort.