Ear-and-Mouth

Ear-and-Mouth
Ear-and-mouth (E&M) offers a more advanced solution than either the FXO or
FXS ports, as well as several features that the other two do not, such as trunking
and either analog or digital transmission. E&M utilizes an RJ-48 port as opposed
to the RJ-11 used by the others. Cisco routers would most likely use an E&M
port for connection to PBX or PSTN, as well as a connection requiring
trunking.