Question

The traffic statistics of a company using a PABX indicates that 180 outgoing calls are initiated every hour during working hours. Equal number of calls come. Each call lasts for 200 seconds on the average if the GOS required is 0.05, determine the number of lines required between the PABX and the main exchange.

Answer 1

The number of lines required between the PABX and the main exchange is 400.

The number of lines required between the PABX and the main exchange is 400.

Here's the calculation:

Traffic per hour: 180 outgoing calls + 180 incoming calls = 360 calls per hour

Average call duration: 200 seconds per call

Grade of service (GOS): 0.05

Erlang formula: B = λ * h

Where:

B is the number of required channels

λ is the traffic intensity in Erlangs

h is the average holding time in hours

Calculate the traffic intensity:

λ = 360 calls per hour * 200 seconds per call / 3600 seconds per hour = 20 Erlangs

Calculate the average holding time:

h = 200 seconds per call * 1 call per 3600 seconds = 0.0556 hours

Calculate the number of required channels:

B = 20 Erlangs * 0.0556 hours / 0.05 = 400 channels

Therefore, the number of lines required between the PABX and the main exchange is 400.