An alarm circuit is interlocked with the start circuit of power driven industrial machinery such as a coal tipple so that before the machinery can be started, an alarm must be energized for a predetermined time to alert personnel that the machine is about to start. In the event that the machinery is not started within a predetermined time after termination of the alarm, or in the event that the alarm has not actually sounded, the whole cycle must be repeated.

A visual and audible alarm are connected to a control circuit for an oil well pumping unit. The control circuit includes a time clock which controls the intermittent ON-OFF cycle of operation of the pumping unit in the automatic mode, the OFF portion of the cycle allowing the well to recover pressure. The audible and visual alarm operates through a time delay relay connected to the time clock to provide a warning to people in the vicinity of the pump of the imminent start-up of the pump before allowing the pump to start, thereby providing people in the area the opportunity to avoid injury by evacuating the area.

A time delay and alarm system is provided to ensure safe operation of periodically activated apparatus having potentially dangerous moving parts. The system preferably employs a 555 type integrated timer circuit, a horn, and a pulse generator which causes the horn to produce a cyclical sound.