PD 6561-1992
修改件(草案):BS 6789 Pt.1-84"英國長途通信公共交換電話網(wǎng)連接用單功能或多種特別功能裝置.第1部分:一般要求規(guī)范"
A draft amendment to BS 6789:Part 1:1984 "Apparatus with one or more particular functions for connection to the British Telecommunications public switched telephone network. Part 1. Specification for general requirements"