Tom's idea is good, there's a lot to know about Group Calling.
However, to do what you want, I would do it like this:
(In fact, last week I set one up just like this)
Put your agents in the Calling group.
Set the group type for "SUTO LOG OUT"
Set the OVERFLOW for that group to go to Voice Mail, set the TIME BASED to Overflow to 25 Seconds (About 4 Rings, this can be adjusted) Set the NUMBER BASED to 99.
For now, leave the PROMPT BASED Alone.
Also, set the QUE ALARMS like this:
Threshold 3 = 3
Threshold 2 = 2
Threshold 1 = 1
Make the MESSAGE RECEIVER for the Calling Group the AGENT who's Light you want to Light up.
IN VOICE MAIL - Create a MAILBOX for the CALLING GROUP (i.e.; Calling Group = 775, make a mailbox 775)
Put an ES2 button on the agent's phones.
Also, put a Button (*22) on each agent's phone for the CALLLING GROUP. (i.e.; *22 775, for group 775)
When you get this done, HERE's HOW IT WILL WORK:
FIrst, youir agents MUST UNDERSTAND THAT THEY ARE RESPONSIBLE TO ALWAYS MAKE SURE THEIR ES2 (LOGIN) BUTTON IS LIT WHEN THEY ARE AVAILABLE.
When the office is dialed, the Auto attendant answers and asks for an extension. (OR you could have a MENU PROMPT/SELECTOR CODE) Route to the CALLING GROUP NUMBER (i.e.; 775)
The ext for the DGC group is dialed, the calls will then route to an available agent.
OK, HERE's where the Group Calling Features Kick IN:
If there isw an available agent, that agent will get the call.
-OR- IF their are no agents avaialble, the call queue light lites up, blinks slowly for 1 call in q, blinkjs fast for 2 calls in q - and goes solid for 3 or more.
ALSO - after the overflow TIME is met, it goes to voice mail.
NOW, MORE MAGIC:
If there are 2 agent avaialble, and the agent that received the call DOES NOT ANSWER, after about 6 or so rings (NOT ADJUSTABLE) the receiving agent will be LOGGED OUT, and the call will be sent to the other available agent.
-OR- IF, On the other hand there is only 1 agent, and he does not answer, after 6 or so rings HE WILL BE LOGGED OUT, and the call will IMMEDIATELY go to Voice Mail.
THe person whose phone you designate as the MESSAGE RECEIVER will have their MESSAGE LIGHT turned on when a call is sent to the VOICE MAIL of the CALLING GROUP.
They will have to log into Voice Mail with the CALLING GROUP's NUMBER to get the message.
If no one answers the calls need to route to an agent's Mailbox.