DID is the ability to route calls form the PSTN directly to extensions of a PBX or a Call Manager. With DID enabled, there is no need to use an operator or a Call Attendant to forward calls to internal extensions.Instead you can route directly to people’s extension.
Here we are. In one week at this time , I will be sitting in the exam class.
I’m still confident to pass it next friday, for the moment no project to reschedule but will put the pressure on this last week to be ready for the exam. So If I see Wednesday that it is too short then I’ll take the decision at that moment.
We will see…. 😉
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 !
FXS is an RJ11 interface which is connecting a phone, a fax,… In contrast with FXO, FXS provides dial tone and ring voltage.
FXS can use also the same signaling ( loop-start and ground-start) but loop-start signaling is preferred on FXS line.
FXO is an RJ11 interface which is providing a connection to a PSTN Central Office (CO) or to a PBX interface.
A FXO is considered as a telephony line. We can then find 2 types of signaling :
- Loop-start signaling : this is a type of supervisory signaling that allows indication of on-hook and off-hook states. But this signaling is vulnerable to a condition knows as glare that involves 2 endpoints seizing a trunk a the same time.
- Ground-start signaling : Same as loop-start signaling but this time we suppress the glare effect on these lines.
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