Hi All, I've been watching this thread with great interest. I have limited experience in with the design of circuits but have a lot building them, hence not actually getting involved until now. One thing we all know if that wireless comes are very VERY expensive but would be extremely handy for the likes of SM's and the crew etc. One thing I have recently attempted is to link a cheap Bluetooth Motorcycle headset to the Tecpro AD903 2 to 4 wire unit. It apparently connects all sorts of I/O impedance's and devices to the ring with lots of adjustment. The BT headsets themselves work over quite a distance (1200m claimed outdoors) 400m actually tested with caravans in the way in a caravan park. They are extremely clear and allow duplexing. They have a 4pin 3.5mm jack on them, using the screen as a common for both the left/Right channels and the Mic. I seem to have found that when plugging this into the AD903 it does not like it at all and I have had a whole host of issues, ie, cross talk between the headphones and microphone, a very quiet level from both the microphone/headphones and the return from the ring. In theory this should be straight forward as I am using a 4 pin XLR to 4pin jack and connecting as per the AD903 "unbalanced connector instructions". I think the problem I am having is the combined screen. I then noticed that some people are using a mini jack on the bluecom system and wondered if a bluecom beltpack would give me the answers. First off, do the blue com work with tecpro, or would I need to replace our system? Secondly, what is it that allows the use of a low impedance headset and 4 pin jack inside of the bluecom? Thirdly, does anyone have any PCB's for the beltpack for sale? I may need to build one if it is compatible with tecpro system in some way. Has anyone else tried something of this nature, or have any idea what my next port of call could be? If I can get this working I will be sharing it on here just as a little blog or post of some kind. Thanks in advance.