retentive and non-retentive coils. Computer terminology.

[Nat]

Никак не могу сообразить, что-бы значило слово coil в данном контексте:

Coils are used to control discrete references. Conditional logic must be used to control the flow of power to a coil. Coils cause action directly; they do not pass power flow to the right. If additional logic in the program schould be executed as a result of coil condition, an internal reference schould be used for that coil or a continuation coil/contact combination may be used.
Coils are always located at the rightmost position of a line of logic. A rung may contain up to eight coils.
The type of coil used will depend on the type of program action desired. The states of retentive coils are saved when power is cycled or when the PLC goes from STOP to RUN mode.The states of non-retentive coils are set to zero when power is cycled or PLC goes from STOP to RUN mode.

[rslon]

Вот что сожно найти в Гугле:

Coil - это, условно говоря, вылетающая "пробка", поставленная в схеме контроллера, причём позволяющая программе устроить "обработку" своего срабатывания как события. "Пробка" может, когда после остановки мы вновь запускаем процесс, либо запомнить своё состояние до остановки (retentive) или нет (nonretentive)

Nonretentive coil: A coil that will turn off upon removal of applied power to the CPU
Retentive coil: A coil that will remain in its last state, even though power was removed.
источник: http://support.automationdirect.com/docs/glossary.html