Two connections are established for each call with an IP phone on the 'LAN/WAN' port.

Therefore, you can only conduct up to three calls concurrently with IP phones. Additionally, the total number of possible calls is reduced.

Examples:
Calls are being conducted with two IP phones. Then two additional calls can be made using the other interfaces.
Calls are being conducted with three IP phones. Then no additional calls can be conducted using the other interfaces.

You can conduct up to three calls simultaneously with cordless phones that are registered with the FRITZ!Box.

Examples:
Calls are being conducted with two cordless phones and an IP phone. Then two additional calls can be made using the other interfaces.
Calls are being conducted with three cordless phones and an IP phone. Then one additional call can be conducted with an analogue phone, or the integrated answering machine or the fax can accept an additional call. No additional call can be conducted with an IP phone.

You can conduct one call with each analogue device connected to the 'FON' socket.

The answering machine and the fax can each accept one call. All other callers hear a busy signal, even if you set up more than one answering machine. You cannot send a fax while receiving a fax, and you cannot receiving a fax while sending one.