Подчеркните конструкции с неличной формой глагола.

1. The impression of bar codes on letters is considered to be one of the basic
methods of achieving mechanization in the post service.
2. The load is a resonant circuit tuned to the frequency of the signal applied to the
input of the stage, this resonant circuit being either a single tuned circuit or a band-
pass filter.
3. Radio frequency amplifiers in which single-tuned circuits serve as a load are
known to be tuned amplifiers.
4. Visual communication allows misunderstandings to be instantly corrected.