To better answer your question, let's break down some key concepts related to call queues:

1. Call Queue: A line of waiting calls that are being held until an available agent is present to take them.

2. Agent Alert Time (AAT): The time interval between when a call reaches the next agent in a serial queue and when they receive a notification about it.

- If you set Agent Alert Time for 30 seconds, then after each agent finishes with their call or completes their work period, there will be an idle wait of 30 seconds before another alert is sent to them.

3. Call Forwarding (CF): This refers to what happens when a certain condition is met while the call is still in the queue.

- For example, if you set Call Time Out Handling to forward calls after 2 minutes and no agent answers or becomes available within that time frame, then those incoming calls will be forwarded according to your CF rules.

4. Call Queue Logic: This refers specifically to how Teams handles situations where multiple agents are in the same queue but there aren't enough resources (i.e., lines) for all callers at once.

- There are two main types of call routing logic used here:

a) Circular Routing: Calls will keep going around through each agent until either an available line becomes free or if you've set a specific number of attempts before forwarding to another destination like voicemail.

5. Call Time Out Handling (CTOH): This setting determines what happens when no one answers after a certain amount of time has passed while waiting in the queue.

- If CTOH is enabled, then once this period expires without anyone answering or becoming available again due either lack of availability themselves; then further actions may include:

i) Forcing calls into voicemail

ii) Forwarding them to another number/extension etc.

Now let's apply these concepts back to your specific scenario:

1. Initial Call Handling:

- A caller dials the call queue extension.

- The first two agents receive a ring for their respective alert times (30 seconds each).

2. If both Agent 1 and Agent 2 are busy or have their status set as 'Do Not Disturb,' then:

i) Assuming serial routing is still active, after exhausting all available agents within the defined call queue settings:

- The next caller will receive a ringback tone until either an agent becomes free.

- If no additional resources become available and if you've configured it so (e.g., via Call Time Out Handling), then calls may be forwarded to voicemail or another destination.

3. Call Queue Overflow Behavior:

- This depends on how your call queue is set up but common behaviors include:

i) Busy Tone: All subsequent callers will hear a busy tone indicating no agents are available.

ii) Call Back/IVR Menu: An IVR (Interactive Voice Response) menu can be triggered to offer options like leaving a voicemail, calling back later during business hours etc.

To find more detailed documentation on this subject, I would suggest checking out the following resources:

1. Microsoft Teams Phone System Documentation: This is Microsoft's official resource for all things related to their phone system features including call queues.

- Specifically look under 'Call Queues' and then drill down into topics like 'Queue settings', 'Agent experience', etc.

2. Teams Administrator Help Center: While not exclusively focused on the technical aspects of call queueing, this site covers many administrative tasks including setting up and managing phone features in Teams environments.

- Search for keywords such as 'call queues,' 'agent alert times,' or 'Call Time Out Handling' to find relevant articles.

3. Microsoft Community Forums: Sometimes asking a specific question on dedicated forums like these can lead you straight to the right person (or documentation) who knows exactly what's going on with your particular setup.

- Make sure to include all necessary details about your environment, configuration settings etc. so others can provide accurate help.

I hope this information helps clarify some of the key concepts and behaviors surrounding call queues in Teams! If you have any further questions or need additional clarification feel free to ask.