Hi,
Fxo and e&M are two different interface with totally different signalling.
An Fxo simulates a phone to the Pstn or to an fxs port on the PBX
allowing users behind that fxo port to dial out to the pstn or through the pbx.
They however do not support dial-in as the dont play dial-tone or collect digits inward but
can be trunked to an alternate fsx port
with a phone hanging off it to answer inwards calls to that port( single phone number).
E&M using ear and mouth signalling and can play dialtone and collect digit in either direction.
they are always connected to an E&M speaking neighbour and
is always the way to go when you're thinking of bi-directional communication.
