The DECT phone displays strange characters or does not ring
If when a call comes in the phone displays strange characters, does not ring, or behaves abnormally (e.g. after the call does not recover again), it is possible that it is experiencing a buffer overflow due to the information about the identity of the caller that the PBX passes to the telephone and that the DECT base passes unaltered. This phenomenon can occur with telephones other than system telephones (eg Siemens / Gigaset).
VOIspeed passes the caller information in the SIP packet to the terminal, exactly in the FROM field of the INVITE packet sent to the terminal, such as:
From: "Test 1234567890123456789012341 - Amministrazione"<sip:firstname.lastname@example.org>;;tag=7E666E7D
In the case of an internal call, the PBX sends a string of the type “name surname – department“, in the case of an external call from a contact stored in the directory, “name surname – company” is sent.
Now if this string is longer than what the terminal can handle, the latter can overflow, manifesting the symptoms already described.
We have seen that in several Gigaset models this limit is 41 characters. Since Spectralink does not provide support on non-system terminals, the only way to avoid the problem is to make sure that the total number of characters in the string is less than or equal to 41 characters. To do this, you can limit the number of characters for the department (for internal calls) and for companies (for external calls).