NEXT month Hong Kong will start the first Asian trial of video down the telephone line. The three-month technical trial in 50 homes of Hongkong Telecom employees will be followed by a three-month test in 400 households of every income band. The guinea pigs will be offered 100 hours of films, features, children's and educational programmes, documentaries and musicals, but will still have to pay for the service. ''You pay for what you see. We are trying to gauge what people will watch or what they will pay in a real life situation,'' says HK Telecom director of multimedia services, Dr William Lo. The company would pick 15 to 20 housing blocks and then ask about 20 households to try it out, said Dr Lo. Prices were not yet fixed but would probably fall into three bands, with a monthly fee of between $80 and $180, and a per-view cost of $18 to $25, he said. The trials would cost the company $60 million, said a HK Telecom representative. Dr Lo thought the service would succeed in Hong Kong, where 5.8 per cent of the gross domestic product was spent on entertainment compared with about two per cent in the United States. In video-on-demand, television shows are beamed down the telephone wire to a modem and decoder on the TV, doing away with the need for a video recorder or player. For the trial, the telephone company will provide the IBM equipment, which is about half the size of an A4 book. Telephone calls can be made and received during transmission, even though the phone line is in use all the time. The first trial of the technology was carried out in the US a couple of months ago.