HC Deb 22 July 1968 vol 769 cc47-8W
Mr. Roebuck

asked the Postmaster-General what progress is being made with research into line of sight telephone transmission.

Mr. Stonehouse

To provide for the growth of telephone traffic on the microwave trunk network, and to meet demands for services such as data, view-phone and television transmission, my Department is conducting research on new types of microwave system on frequencies hitherto unexploited, above 10 GHz, since the available spectrum below 10 GHz will be exhausted in a few years' time. We are collaborating with the Radio and Space Research Station. Slough, in studies to determine the effect of rain and fog on the propagation of these radio waves. We are developing equipment based on the use of microelectronic circuits and pulse-code modulation techniques.

The possibilities of optical beam communication through the free atmosphere have also been considered, but this seems less attractive than the use of microwaves, because of the severe effect on the signal strength of rain and fog. For this reason our research on optical sys tems is now aimed at the propagation of light waves on glass fibres.