Alan, even though you advocate the time delay photo electric sensor, I personally do not think they are as good as a manual style time delay with instant PES. A manual style time delay you can adjust it from one second upwards 180 seconds. The reason why I am putting two timers in my system is one timer will be set to 15 seconds and this will trip a strobe light in the shop. The second one I will set at one minute + and this one will shut down the contactor. False alarms can be identified safely without losing suction. This is why I decided to go with lit semitransparent drum for quick reference. If there is a false alarm the strobe light would warn you and then you can ease up on the planer with sufficient time before a complete shutdown.