The Allen-Bradley 849-ZAA32 Pneumatic Timing Relay is a type of electrical switch that is driven by an external signal that is applied to its coil. This relay is part of the 849 Timing Relays series and it comes from the factory with a normally open, on-delay configuration, and this means that the Allen-Bradley 849-ZAA32 Pneumatic Timing Relay will wait for a configurable time span after its coil is energized to change its status from open to closed. The electrical contacts in this pneumatic pressure relay are rated for working with either 220 Volts AC voltage at 50 Hertz or a 240 Volts AC voltage at 60 Hertz. The length of the delay can be manually configured by adjusting a screw-type needle valve, from 0.05 to 180 seconds. Given the sturdy materials that the pneumatic timing relays are made of, they can be deployed in both indoor and outdoor applications.

A key feature of the Allen-Bradley 849-ZAA32 Pneumatic Timing Relay is that the final users can manually change the switch configuration from an on-delay configuration to an off-delay configuration with some minor adjustments in the mechanisms. When the Allen-Bradley 849-ZAA32 Pneumatic Timing Relay operates with the off-delay configuration, it will change its electrical status only after the coil is de-energized and the user-configurable timespan has been completed. The most common applications for this type of pneumatic timing relay are in industrial systems in hazardous or flammable environments where electronic timing relays may be damaged, and the use of electro-pneumatic relays like the 849-ZAA32 Relay is recommended to avoid the risk of creating electrical sparks which could cause a fire or explosion.