Abstract: A telephone unit adaptable for either wall or desk top mounting has a retractable bracket, slidably mounted in a recess in the bottom surface of the telephone unit base. The bracket has a head portion having a keyhole aperture for fitting over a screw or similar item on the wall, and a stem portion slidable longitudinally in the recess. Two bosses formed on the telephone unit base extend through slots in the stem portion and screws in the bosses hold the bracket in position. When extended the head portion extends slightly from the base while in the retracted position the bracket is concealed.

Abstract: A family of RC active filters in which band-pass, low-pass notch, high-pass notch, band-stop and all-pass second order sections may be realized. The filters provide unidirectional functional tuning of the four basic parameters .omega..sub.o, Q.sub.o, .omega..sub.z and Q.sub.z through resistive trimming.

Abstract: For telephone sets and similar forms of apparatus in which pushbuttons are mounted more or less flush with the outside surface and actuated by pivoting, a series of such pushbuttons are mounted on a shaft secured in a housing. The pushbuttons are mounted on the shaft at one end and at the other end rest on pushbutton switch mechanisms. Each button is identical and interchangeable. Locating formations on buttons and housing interengage to locate the pushbuttons. The switch mechanisms are spring loaded and urge pushbuttons to a non-actuated position. Indicator windows for removable and interchangeable indicators can be provided.

Abstract: In a telephone system supervision is provided for, between a local terminal typically associated with a telephone switching facility and a remote key telephone terminal. A data link between the terminals includes a two wire transmission line terminated with hybrid circuitry. The hybrids provide full duplex operation. Electronic circuitry, in the local and remote terminals, operates to provide continuous two way transmission of supervisory data by means of diphase signals. A coded diphase signal transmitted from the local terminal has a baud rate twice that of the conventional diphase signal transmitted back from the remote terminal. This allows simple receiver sync extraction circuitry in both the remote and local terminals. The length of transmission line permissible between terminals is limited by a maximum permissible one way delay of half the period of the maximum baud rate.

Abstract: A converter power supply is provided with a novel current regulating circuit. A magnetoresistive element is disposed in flux coupling proximity to the output inductor of a power supply for providing a control signal corresponding to the output current thereof. The element is mounted in the air gap of the split-loop core of the inductor.