Repertory dialer with efficient data storage

Abstract

Method and apparatus are provided for microprocessor controlled storage and dialing of telephone numbers and storage and access of associated data. Each entry includes a telephone number field and an associated data field. The two fields are differently encoded and thus enhance the storage efficiency by avoiding a requirement for field terminating characters. An operator provides particular entries which are matched with stored fields of associated data. Upon determining a match, the stored associated data is displayed and the associated telephone number may be automatically dialed. A three chip microprocessor set scans a keyboard, controls displays, and communicates with program and data storage units. The microprocessor is used in conjunction with integrated circuitry to detect the existence of a dial tone for a predetermined time. Multifrequency or pulse dialing of a number from storage may be effected by the inventive dialer. An interface circuit includes muting circuitry for either multifrequency tones or pulses. A power supply circuit includes a trickle charging circuit for battery backup and circuitry to prevent access to, and alteration of, memory storage in the event of power failure. An audio circuit includes directional coupling to minimize audio feedback in a speakerphone mode of operation.