Abstract: A rotatable coupling for audio cables is shown having a stator and a rotor divining an electrical rotary interface (301) for providing continuous connection between audio cables. A protective stator housing (304) retains the stator and a protective rotor housing (305) retains the rotor. A rolling-element bearing (306) with an inner race and an outer race allows the protective housings to axially rotate.

Abstract: A rotatable coupling for audio cables is shown having a stator and a rotor divining an electrical rotary interface (301) for providing continuous connection between audio cables. A protective stator housing (304) retains the stator and a protective rotor housing (305) retains the rotor. A rolling-element bearing (306) with an inner race and an outer race allows the protective housings to axially rotate.

Abstract: The thermionic valve tester (10) has a casing (11) and three valve sockets (12) each of which is adapted to receive and has terminals for connection with the electrode pins of different types of thermionic valves. The thermionic valve tester (10) also has a display (13) comprising a series of LED lights, three user operated buttons (16), and a single power supply socket or terminal (14) which supplies power to all components of the valve tester and which is adapted for connection to a low voltage DC power supply lead. Internally, the thermionic valve tester (10) has a plurality of voltage regulators each with a switchable connection to at least one valve electrode terminal of the valve sockets (12) and a memory in which is stored the tests and the performance criteria for different types of thermionic valves.

Abstract: The thermionic valve tester (10) has a casing (11) and three valve sockets (12) each of which is adapted to receive and has terminals for connection with the electrode pins of different types of thermionic valves. The thermionic valve tester (10) also has a display (13) comprising a series of LED lights, three user operated buttons (16), and a single power supply socket or terminal (14) which supplies power to all components of the valve tester and which is adapted for connection to a low voltage DC power supply lead. Internally, the thermionic valve tester (10) has a plurality of voltage regulators each with a switchable connection to at least one valve electrode terminal of the valve sockets (12) and a memory in which is stored the tests and the performance criteria for different types of thermionic valves.

Abstract: The audiovisual teaching apparatus (2) for demonstration purposes before a group of students has a frame (6) on which is mounted a board (4). The front surface of the board (4) includes an area (5) treated to function as a whiteboard surface on which standard dry-maker pens can be used to removably write and draw on the surface. The whiteboard surface (5) is pre-printed with a plurality of musical staves (8) and has an array of substantially parallel conductive tracks aligned with the lines and spaces of the musical staves (8). The conductive tracks are connected to sound reproduction apparatus and a hand-held wand (24), which includes a localized antenna, is adapted to select an individual line or space of the musical stave (8) so that the selected note is played by the sound reproduction apparatus.

Abstract: The audiovisual teaching apparatus (2) for demonstration purposes before a group of students has a frame (6) on which is mounted a board (4). The front surface of the board (4) includes an area (5) treated to function as a whiteboard surface on which standard dry-maker pens can be used to removably write and draw on the surface. The whiteboard surface (5) is pre-printed with a plurality of musical staves (8) and has an array of substantially parallel conductive tracks aligned with the lines and spaces of the musical staves (8). The conductive tracks are connected to sound reproduction apparatus and a hand-held wand (24), which includes a localized antenna, is adapted to select an individual line or space of the musical stave (8) so that the selected note is played by the sound reproduction apparatus.

Abstract: Controlling the performance of the thermionic tube (102) having a cathode (103), a plate (104) and a grid (105) is disclosed. The tube is configured to provide amplification of an audio derived signal (106) and is arranged to apply a grid bias voltage to the grid. The absence of an input audio signal is detected whereafter output current between cathode and plate is measured to identify actual output current. The actual output current is compared against a preferred output current and the grid bias voltage is adjusted so as to bring the actual output current value towards the preferred output current value.

Abstract: Controlling the performance of the thermionic tube (102) having a cathode (103), a plate (104) and a grid (105) is disclosed. The tube is configured to provide amplification of an audio derived signal (106) and is arranged to apply a grid bias voltage to the grid. The absence of an input audio signal is detected whereafter output current between cathode and plate is measured to identify actual output current. The actual output current is compared against a preferred output current and the grid bias voltage is adjusted so as to bring the actual output current value towards the preferred output current value.