Grounding of Alarm Panels

National Electrical Code Requires our Alarm Equipment to be Grounded.
How do we know what size conductor to use?

NFPA 70 2002 states in Article 250.122: Size of equipment grounding Conductor:

(A) General Cu, Al, or Cu-clad Al equipment grounding conductors of the wire type shall not be smaller (2008 NFPA 70 adds: but in no case shall they be larger than) than the circuit conductors supplying the equipment

TABLE 250.122 Minimum Size Equipment Grounding Conductors for grounding equipment Rating or setting of Automatic Overcurrent Device in the Circuit AHEAD of Equipment:
Not Exceeding: (AMPERES) 15 :   14AWG Cu  or 12AWG Cu-clad or Al
Not Exceeding: (AMPERES) 20:    12AWG Cu  or 10AWG Cu-clad or Al

So for our Security, CCTV and Access Systems Supplied by Class II Transformers, we first size it by the Equipment Grounding Conductor in the Supply Branch Circuit: 14AWG(Cu) for General Lighting Circuits and 12AWG(Cu) for Dedicated Branch Circuits.
For Fire Alarm Systems supplied by a Dedicated Branch Circuit, that Circuit must be 20A so our minimum size grounding conductor is 12AWG(Cu)