на плате тоже должен быть CLIP

Я не уверен что на релизе 4.х проц сможет выдернуть аон с аналогового транка без clip

ПО крайней мере, в доке на пятый релиз так написано:
The CLI (Calling Line Identification) feature for APA (Analog Public Access) and AMIX/AMIX-1
(Analog Mixed Line) boards allows the caller number to be received through the analog
switched public network.
This feature is based on the CLIP (Calling Line Identification Presentation) additional service;
the CLIP information is transmitted via FSK (Frequency Shift Keying) asynchronous signals in
on-hook mode (during ringing).
The FSK signal can be detected in two different ways: centrally at the CPU level or locally via
the APA board (CLIDSP daughter board).
Depending on the detection type, the system must be equipped with:
- local detection: the APA boards must be equipped with the CLIDSP daughterboards.
Note:
5 APA boards per module, with or without CLIDSP daughterboards; one CLIDSP daughter board for
8 accesses.
- central detection: no special hardware. 6 incoming calls may be handled simultaneously.

С плюсиком обычно идет в сторону SIP, а не в сторону аналоговых линий.