Abstract: An annunciator and/or shut-down system for an automatic processor for treating tissue specimens. In a tissue processor of the type wherein the reagents are drawn from reagent containers into the reaction vessel by drawing a vacuum on the vessel and reagents are returned to their respective reagent containers by gravity, the filled or unfilled condition of the reaction vessel is determined by sensing the vacuum condition during two time intervals; one near the start of filling and one just after filling is normally completed. The vacuum condition indicative of a filling or filled vessel differs for each sensing time interval. Logic circuitry analyzes the sensor condition for the specific time interval and, if the condition is maintained over a predefined delay period, outputs a short duration shut-down signal which causes latching of a mechanical shut-down and/or annunciator switch.