Emergency Responder Question

[rgmasbad]

I will be implementing ER and want to specify specific rooms with one (1) IP phone with a single DID as their own ERL. I was told that I will need to configure each IP phone with a minimum of two DID numbers or add a second office with another IP phone to make this work.

Can someone explain to me why I need two DIDs for this to work? How is the ER server processing a 911 call that it needs two DID numbers?

Thank you.

[koenigr]

It's my understanding that the 2 DID / ERL is more of a best practice. Because with only 1 DID/ERL if a second call is made from that ERL the phone mapping is overwritten.