a call processor in an exchange requires 120 ms

Question

A call processor in an exchange requires 120 ms to service a complete call. What is the BHCA rating for the processor? If the exchange is capable of carrying 700 Erlangs of traffic, what is the call completion rate? Assume an average call holding time of 2 minutes.

Call service time= 120ms

BHCA-(60X60)/ (120X10^-3)=30,000

t_h =holding time 2 minutes

A_o=mean effective traffic carried through the network=700 Erlangs

A_o==Co X th ,

Here

C_o=mean effective traffic rate

Therefore Co = A_o/ t_h =700/2 per minute= 21,000 calls per hour

Therefore total call attempts in Busy Hour= 30,000

And number of successful calls= 21,000

So, CCR= 21,000/30.000 = 0.7