do duty (verb) function: perform, work
Sinonime: at intervals, at times, every now and then, every once in a while, every so often, from time to time,
hardly, infrequently, intermittently, irregularly, not often, now and again, occasionally, off and on, on occasion, once and again, once in a blue moon, once in a while, once or twice, periodically, sometimes, sporadically
Antonime: idle,
malfunction