Abstract: A telephone, for use in a key telephone system, has built-in test capability for verifying the operation of components in the telephone. The test capability is such that a relatively unsophisticated user can step through and conduct each of a plurality of separate tests. Interface to the tests is provided through the same switches and indicators on the telephone used for normal telephone operation. Status of certain test routines and components being tested is indicated, during the test mode of operation, on the telephone's regular indicator lamps.

Abstract: A programmable key telephone system has a key service unit with a plurality of telephones coupled thereto. The key service unit is controlled by a microcomputer. An alphanumeric display mounted in the key service unit is coupled to the microcomputer and is driven during an installation mode of operation to prompt an installer through a sequence of steps designed to elicit instructions for programming system features. A telephone from the key telephone system is coupled by the installer to the microcomputer and used as a data input terminal to enable the installer to input instructions via the telephone's keys. Non-volatile memory is coupled to the microcomputer for storing system feature data in accordance with instructions entered by the installer. Indicator lamps on the data entry telephone can provide additional prompting or feedback to the installer as to features being programmed. Programming of the system can be accomplished without interrupting normal telephone operation.

Abstract: A key telephone system uses four wires for transmission of voice and audio signals to and from the telephone stations and other components which are part of the system. A plurality of telephone stations are provided, each having a two wire audio input port, a separate two wire audio output port, and a data port. Communcation paths are established through a crosspoint matrix. The matrix includes a first group of addressable crosspoint switches for coupling selected transmit signal paths to selected first link points. A second group of such switches is provided for coupling selected receive signal paths to selected second link points. A third group of such switches couples selected first link points to selected second link points. A link searching routine determines which links are available for effecting communication paths. A minimizing function shares communication paths among common signals when possible.

Abstract: A desk supported telephone set is provided with a case attached to an inclined base adapted to be seated on a horizontal surface to tilt the case and a telephone receiver mounted thereon towards the user. The same case may be mounted on a substantially vertical wall surface by removing the base from the case, rotating it 180.degree. and reattaching it to the case. When the base is mounted on a vertical surface, the case will extend away from the vertical wall surface at an acute angle with the case inclined towards the user for easy access to the receiver seated on the case. To assure that the receiver is held firmly to the case when the set is mounted in an inclined manner on the vertical wall surface, the case is provided with removable, integrally molded fasteners which upon severance from the case can be used to secure the receiver to the case.