Two connections are established when making calls with an IP phone that is configured for the 'LAN/WAN' port. Therefore, you can conduct a maximum of two calls at the same time with IP phones, and the number of possible calls is reduced.

Example:
If you conduct a call with an IP phone, three additional calls can be made using the other interfaces.
If two IP phones are being used to conduct calls, one additional call can be conducted using the other interfaces.

You can conduct a maximum of three calls at the same time using cordless phones that are registered with the FRITZ!Box's DECT base station.

Examples:
If three cordless phones and an IP phone are being used to conduct calls, you cannot conduct an additional call using the other interfaces.
If calls are being made with three cordless phones and an analogue phone, the integrated answering machine or the fax can accept an additional call. You cannot conduct an additional call with an IP phone.

You can conduct one call with each analogue device connected to the 'FON 1' or 'FON 2' 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.