Задание 3 к тексту Some Facts about Frequency
Найдите в тексте следующие словосочетания, скажите, какой формой глагола являются слова с окончанием –ed, переведите их:
isolated AC generating schemes; frequencies based on convenience for steam engine; frequencies were used on different systems; world being divided into two camps; AEG decided on 50 Hz by 1899; the turbine speed had already been selected; project had already been specified at a speed; 25 Hz prevailed as the North America standard; the installed base at 25 Hz.