Typically, these figures can be misleading. Often, they are calculated under the best of circumstances (i.e. the PBX is equipped with the fastest processor, maximum number of DTMF receivers, and largest amount of memory), and may not reflect your configuration. However, generally, they are a means of evaluating the pure call processing horsepower that the switch can provide. BHCA simply refers to the number of calls that the system is capable of processing in it’s busiest hour of traffic, while BHCC refers to the number of calls that the system is capable of terminating under this busy hour load. Unless you’re a call center, hospital, or municipality, most PBXs from the major manufacturers (i.e. Nortel, Avaya, NEC, etc.) are more than adaquate at processing the average office call load. Purists may disagree, but these statistics are often secondary buying decisions. I’d only worry about it if you’re in a particularly heavy calling environment.