電磁ロック = EM Lock
駆動出力 = Driving Output

The biggest issue of the translation is how to clarify subject/object relationship in acceptable length of target term. The source term means "output (from the other device) to drive em-lock".

EM-lock => 電磁ロック or EMロック
output => 出力

The difficulty of translation is focused on the main verb "driving". If we simply use 駆動, there is a possibility to misunderstand like 電磁ロック（が）駆動（する）（シャフトの回転などの）出力. If 駆動用, there is still ambiguousness to be able to take（何かの装置を）電磁ロック（により）駆動（するために）用（いる）出力. This problem is almost the same in cases of 作動 and 作動用.
So I finally chose 開閉制御用. Is this a self-satisfying work of translator or effective contribution to the reader's understanding ?
I'm confident 電磁ロック開閉制御用出力 never misleads readers, but I'm not confident everyone think this term is friendly or not.....


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Note added at 3 hrs 51 mins (2005-09-06 07:59:06 GMT)
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I change my mind. 制御 is redundant because it implies 出力 could be signal or a signal line. The asker's description that "output" is "Amount of energy" means it must be energy or a power line. Thus, now I think 電磁ロック開閉用出力 is better.