focus to image receptor distance | source to image distance | FID [Abbr.] | SID [Abbr.]

image distance | photo-principal distance | principal distance

Table 1 Current provisions concerning use of cable TV networks for the provision of telecommunications services can be summarised as follows: Use of cable TV networks for liberalised services Belgium No Denmark No France Non-voice services only Germany No Greece ---------* Ireland No legal provision Italy ---------* Luxembourg No legal provision Netherlands Limited use Portugal No Spain No UK Yes Source: "L'impact de l'authorisation de la fourniture de services de télécommunications liberalisés par les câblo-opérateurs", IDATE, 1994, and additional analysis * No cable TV networks available Table 2 Minimum Capacity requirements (approximate) for services Speech: 64 kilo-bits/second ISDN: 140 kilo-bits/second Standard quality moving images: 2 ...[+++] mega-bits/second Enhanced quality moving images: 10 mega-bits/second Table 3 Technical limits on network infrastructure to the home i. Twisted Copper pairs: used by TOs to connect end users to the local switch: up to 257 kilo-bits/second: reliable service to all customers on local network the greater the capacity requirement above 257 mega-bits the greater the trade-offs of increased error rates, lack of reliability and limits on the distance which the end user can be from a central switch.