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

Example:
If you conduct a call with an IP telephone, two additional calls can be made using the other interfaces.
If two IP telephones are being used to conduct calls, no additional calls can be conducted.

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

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

One call can be conducted with each of the analog devices connected to the socket "FON 1" or "FON 2".

A maximum of two calls can be conducted at the same time with ISDN devices connected to the "FON S0" 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.