microfilter and ringer bell

Have set up my mum & dads broadband for them but have run into a problem.
Have put a filter on a BT ringer i.e. it's not a phone just a ringing device as my father can't hear the phone unless he happens to be passing when it rings.
Problem is when the filter is added the ringer does not work, does it need a filter. I don't think so as it does not carry any signal down the line but don't want to attach it in case it knackers their connection.

So am I right & it's ok to connect it without a filter or will they have to try to find another phone my dad can hear.

Thanks in advance

The ringer needs the ring circuit. It should not cause problems without a filter but try monitoring te line stats when a call is coming in.

Two possible solutions.

1. Put a phone splitter into the filter where you want the ringer and then fit a modern phone and the ringer to the phone splitter.

2. Use a filtered face plate and that separate the ADSL and phone at teh point of entry. Then ensure the bell wire is connected at all locations.

Got a phone call this afternoon from the parents, after a bit of diagnostics over the phone have come to the conclusion the wiring to the ringer is wrong.
Sure it was Bt who put it in but maybe not so a job for next weekend to check the wiring. Never thought to plug the phone in the socket this weekend as the ringer just worked before, but after a bit of instructions over the phone they plugged in the phone & it's not working. The ringer has now been disconnected till I sort out what's up.
Thanks for the input.