The best drives now average 100,000 hours, or more than 11 years, of constant operation, between failures.

They became operational in 1939 and were in constant operation for the duration of the war.

There would have been thousands in constant operation throughout the quadrant.

The non-profit Masquers have been in constant operation since 1955.

From here on, the ship's radio com will remain in constant operation.

There were twenty-three of them, all in constant operation.

She said that producing books has become "a constant, long-day" operation.

The physical operation of the city's port, constant and quite unthinkably complex, is managed by another system.

Many of the Austrian tramlines have been in constant operation since they were first opened.

Above all, keep your radio in constant operation from now on.