I am sorry to hear that you are having problems with the CLA-40 supplied a couple of weeks ago, we do not often have problems with these. May I ask where in the system you are connecting it - in the line cord or the curly handset cable? (illustration of the correct connection below) Plus you also need to select the correct setting (trial and error is fine) for the switch in the underside.

On a technical note you can actually test the in-line amplifier on your home phone - but you must keep the volume of your amplified phone low. You are correct that we do not normally advise using an in-line amp with an amplified phone but only because it won't work louder rather than not work at all.

Assuming that the problem is not connection related (it will be interesting to see if it works OK on your home telephone) please return your CLA-40 - we will promptly investigate what is happening - normally the same day - and assuming it is faulty replace it by 1st class post for next day return to you. From experience we find a notable number of returned items are not faulty and are actually caused by other factors. Our approach of 'test before replace' allows us to provide you the best chance of our supplying you a replacement that will work.