E&M stands for a lot of Acronym like

  • Ear an Mouth
  • Earth and Magneto
  • Receive and Transmit

E&m uses an RJ48 interface and is often used to provide tie-line connectivity to PBX. there are 5 types of E&M Interfaces ( I, II , III , IV, V) which are all supported by Cisco except the Type IV.

On this line , we can find the following signaling :

  • Wink-start
  • delay -start
  • immediate-start
  • tone-start

Need to more explanations about the different modes !