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 !