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Appendix A - cost of ISDN calls

The cost of an ISDN call is proportional to the bandwidth and the length of the call. If an MCU used to control a multi site call the booking charge for the device must be added to the cost.

The booking charge for an MCU depends on the data rate, the number of sites (or ports) using the MCU and the total number of port hours per month. This varies from 40 per port hour (70+ port hours per month at 128kbps) to 75 per port hour (1-19 port hours per month at 384kbps). Added to this is a one-off registration fee of 75 per site.

The table below shows the cost for one hour sessions at four different data rates. The first three sessions are for local call charges which would be charged between two London University colleges. The second session is a three site booking which uses the two Ascends and a quad split at UCL to combine the pictures. The third session uses an MCU for switching video.

Number of sites    Remote site     128kbps     256kbps     384kbps     ISDN 30
2                  Local           4.16       8.32       12.48      124.80
3                  LIVE-NET        8.32       16.64      24.96      249.60
3                  MCU             177.48     219.96     262.44      N/A
2                  Europe          100.48     200.96     301.44     1507.20
2                  USA             134.68     269.36     404.04     2020.20
2                  Australia       222.68     445.36     668.04     3340.20
2                  Japan           353.88     707.76     1061.64    5308.20


The cost of booking a satellite transponder and corresponding uplink is approximately 1250 to 1500 per hour. This gives a broadcast quality signal albeit only one way. Since the cost of an international ISDN 30 call is at least 1500 per hour under certain circumstances a satellite circuit can be cheaper. If confidential matters are to be discussed encryption may be provided on a satellite circuit a cost of 200 per hour. Encryption is not needed for ISDN calls since it is not a broadcast medium.

Since LIVE-NET has a direct fibre connection to the BT tower from where video signals can be sent to uplink stations satellite broadcasts are relatively straightforward.

LIVE-NET does not have access to ISDN 30 these figures have been included for comparison purposes only.


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