Hi Ingo,

The phone I'm using is new (not sure what the model number is) and it uses a 4 pole socket but using a 3 pole plug should work 'cause when I plug it into the phone it recognises that a handsfree is in use.

I've connected the mic- to ground in my circuit and used the output direct from the ISD4004 but no good yet. The output from the ISD is quite low - I haven't measured it but I think it's only around 30-40mv. The gain from the opamp is about 10 so the output is quite a bit higher there.

Even so, I still get nothing out of the phone.

I'm going to keep experimenting - I should get it soon.

If I plug an earphone into the socket I should be able to hear if something is going into the mic should i not? That way I can save some money by not having to call the mobile to test it.

Thanks again,

Regards

Tony