Adds two analogue trunk lines. The Caller ID feature (CLIP/CNIP) ensures you benefit from ISDN extras even with an analogue line. Analogue-only operation is possible, but as well mixed mode with ISDN and VoIP trunk lines. Number of modules which can be used in the COMpact 4000: 2 Number of modules which can be used in the COMpact 5200(R)/5500R: 5