Phone handset won't unmute

[speckytecky]

I'm having a problem with the phone unit I use at school. It's a EnGenius EP801 and the Base Unit works fine but the handset will only work on speakerphone - probably something simple I have done to it but I can't fathom out how to get it back to normal. Posting on here in the hope that someone has an answer!

 

Using the handset in speakerphone mode it works perfectly. Turning off speakerphone so that I'm using the ear piece I can't hear any dial tone or voice from the other end but if connected they hear me. I have read the close on 40 page manual but can't find an answer:confused:

[speckytecky]

No one else using these bits of kit then - not surprised as they are close on £500 a Unit! I'm sure it's something in the settings but the 40 page manual isn't easy reading:frusty: