yes, i got the one you mentioned and have wired it into the phone line between the com2400 and the master socket. The master socket end is just a phone plug into a splitter, but that goes into another filter, which is the probable problem. If I wire the alarm into the terminals behind the master socket faceplate, i lose internet. I am going to get a new master socket with an ASDL out and a phone out, I hope that putting a splitter into the phone out for the landline and the alarm might sort the problem. I can live with the error message it reminds me that I need to get round to trying to sort it! But thanks for the info, I did not know I could do that. Cheers again for all the help.