⟩ How many T1 facilities the company needs between its office and the PSTN if it has 47 digital telephones, each operating at 64kbps 3 low-speed video machines, each operating at 384kbps 1 interactive video system, requiring 1.536 mbps.
Need 4 T1's.
Each T1 can accomodate 28 channels.
► 47 digital channels
► 3 low speed V.machines at 384 kbps.
=384/64=6channels
► 1 interactive video systemat 1.536mbps.
=153664=24 channels.
So total=47+6+24=89 channels
each T1 requires 1 synchronizing channel & 1 signalling channel.
So 4 T1 requires 8 channels.
Total=89+8=97 channels.
4T1's =112 channels-96 channels=15 channels(remains free)
