Abstract: A clerk paging system for retail stores wherein a customer can push a "help" button on a call box, there being a call box in each department of the store, and the system automatically provides a stored, paging message to the store's existing paging system, including public address systems and radio systems, the message asking for help at the department in which the customer pushed the "help" button. The system automatically repeats the message with a preset time interval between messages, but only until a clerk pushes a "reset" switch on the same call box upon which the "help" button was pushed. To assist telephoning customers, clerks are paged using a two-part message. The first part of the message, typically a department name, is determined by a button pushed by the store's telephone operator. The system automatically determines the second part of the message, consisting of the telephone line number, by monitoring phone line status. A typical resulting message would be "Plumbing, Line Two".

Abstract: An interdigital electrode transducer mounted on an acoustic surface wave propagating medium having an output proportional to an Nth order derivative of the surface acoustic waves propagating in the medium. The Nth order derivative, where N is any real, positive number, is obtained by using a finite difference approximation. The transducer finger pairs are biphase coded and amplitude weighted in order to detect the proper combination of signal differences for the approximation and thereby indicate the desired derivative.

Abstract: A Content-Addressable Memory Cell featuring a pair of current switches, one at each output of a flip-flop cell to provide for searching the cell at high speed and without disturbing the contents of the cell.