Abstract: A software device to perform math calculations upon numerical or data expressions entries, and capable of coordinating multiple data entries, displays, and storage operations. The package is consisted of dual entry inputs, a single result display, single arithmetic expression display for each entry, and a data spreadsheet matrix which is constantly synchronized with data entries and result contents. The data/arithmetic inputs are entered via the software device control buttons, computer keyboard, software device memory buttons, saved user prior transaction files, the software device entry/result history buttons, or a cut and paste process within the various package displays or external software tools such as Microsoft Office Word and Excel. The software device provides error checking schemes for any type of the above mentioned entry methods in combination with its operation merit monitoring schemes, FIGS. 1 through 21.

Abstract: An air treatment system has a removable and replaceable filter, the filter having a plastic frame, and having a multi-layer filtering medium. A filter seat has a switch located along one side in contact with a flexible tab. When the filter is located in the seat and faces the desired direction, one of two projections on the top and bottom of the filter frame moves the flexible tab to activate the switch, which signals proper installation of the filter. When a filter element is installed, it starts a timer which times the service life of the filter element and an air treatment cartridge. When the timer times out, it signals a user through an LED or audible alarm to replace the replaceable components.