Set them up to use non-overlapping channel frequencies, at least four numbers apart - e.g. channels 1, 5, 9, 13 in a four access points setup. If your environment lets you use wide channels, use 1 and 13 (or 1 and 11 if you are in a part of the world where channels 12 and 13 are disallowed).

Edit: Are you using a WiFi range extender, or a powerline WiFi access point?

Hi Peter M. I'm using a powerline access point.Thanks for the channel suggestion but its not worked. I still get a loss of wifi when I'm located between the two sources (router and TP Link). In addition I've noticed that when I connect through the TP link wifi it is not able to find an IP address. Is there a router setting that permits an IP address to be assigned ?

cheers Nix

Based on your first post my reaction is this: My experience with wifi extenders is that you have to turn off the wifi broadcast on the router itself otherwise since the settings are cloned to the wifi extender, they conflict with each other and cause each other to lose connection due to it repeating the signal. I had to do the same with the powerline adapter I just bought as well. The guest network was being extended and actually showed up twice on wifi devices, so now I'm letting the powerline adapter handle it so I shut the guest network broadcast off on my router. In my routers case, Guest Network is still "on" but the broadcast is disabled. Depending on the router, it may just be simply a "on/off" type thing. I have my regular network still broadcasting though. Powerline adapters work a bit differently though and depending on the type it may or may not work.

However, based on your reply it sounds like it may be a different issue. As per your question, I set my powerline adapter to a static IP and it fixed all the problems I was having. I also reserved (assigned) the adapter IP on my router to make sure it doesn't change. As far as I know, any router can reserve IPs for individual devices but I could be wrong. That may be what you're looking for?

I'm setting my secondary WiFi APs to obtain an IP address via DHCP - and set the main router's DHCP server to assign them a static address. That way you don't end up having static IP addresses programmed anywhere but in the main router.
Then you manually (!) set up the main SSID and password in the secondaries that you have in the main router, just with a different channel. If you copy via WPS, you end up getting the same channel and therefore overlap.