We use a combination of the Motorola XTN446 Link: newbielink:http://www.apexradio.co.uk/motorola-xtn446-two-way-radio-104.htm
[nonactive] and Tecpro/Metro Wired Talkback (Cans), Link: newbielink:http://stage.prepublisher.com/hire/level5.asp?PPL=10690A0A
[nonactive].
The XTN446's are expensive, however you get a good range of about 2-3km, and you can also have a choice of having the roger beep or not. These also include VOX, and you can get a very wide range of headsets, lapel-mics and other types of ear-pieces to go with them. These have now been replaced by the Motorola XTNi, and the XTNiD, however are still available and I would recommend them.
For our communications equipment, we tend to use either Stage Electrics, or Wildtalk, which is a company in York, England. Link: newbielink:http://www.wildtalk.com/
[nonactive]Chris