This invention relates to 3-aryl or heteroaryl-3-alkoxy, phenoxy-, alkylthio- or phenylthiophthalides useful as color formers, particularly in carbonless duplicating and thermal marking systems, which are prepared by the interaction of 2-(disubstituted amino)phenylcarbonylbenzoic acids with an acid chloride or an anhydride of an alkanoic acid in the first step and a further reaction of the product of the first step with an alcohol, a thioalcohol, a phenol or a thiophenol in a second step.

An identification system comprises an interrogator which transmits an interrogation signal to a plurality of transponders, each of which is arranged automatically to reply by means of a first coded identification signal stored in the transponder and modulated onto a carrier wave transmitted by the transponder. The interrogator receives and checks the reply signal. In the event of there being a plurality of transponders within range and broadcasting reply signals simultaneously, the interrogator ...

In a transponder adapted to be attached to an object to be identified, an interrogator for interrogating the transponder utilizes an antenna system including first and second antennae with the first antenna being formed as a loop and the second antenna formed in a figure-8 configuration, and being coplanar with the first antenna. A source of power provides first and second transmission signals to the first and second antennae, respectively. A phase shift is introduced between the first and secon...

An x-y positioning device in which a cable or chain is used to drive a carriage, powered by two motors. The same cable that moves the carriage also constrains the angular orientation of the moving mechanism. In so doing, the moving parts can be made lighter and less expensively, while providing improved dynamics. All is advantageously applied to large, flat-bed plotters, to a computerized engraver, to a large sign painter, or to an elevator.

A central heating control system includes a control panel housing a timer. The timer has three programme sequences for controlling three groups of radiators each group being independently controlled. The control panel also includes switch units which are selectively operable to isolate each radiator. The switch units are triggered by infrared signals transmitted by a portable control unit. The signals may be received directly by the panel or indirectly through spaced windows coupled to the contr...

A noise cancelling system comprises two conventional noise cancelling microphones (1,2) spaced apart by a distance of one of up to 10 cms with use of the microphones (1) being arranged to be close to the mouth of a user for reception of speech and the other microphone (2) spaced therefrom and used as a reference microphone. The signals from the microphones are processed by means (7) which use a batch of signals derived from the reference microphone (2) to modify a signal derived from the speech ...

A roofing structure includes a plurality of beams supporting an inner skin of cladding material. The inner skin of cladding material is secured to the beams by U-shaped brackets. An inverted U-shaped rail nested with pairs of brackets is clamped to the brackets by means of a nut and bolt to define a box-like support structure. An outer skin of cladding material is secured to the rails. Each bracket is provided with locating holes which can be engaged by a bolt and on which the rail can be nested...

A display system including a display device, a storage means having an array of storage locations each location being adapted to contain data representing a visual parameter of a different pixel of a picture to be displayed, and signal generating means for causing the display device to use the data to display a picture. the storage means is adapted to store data relating to a picture of a larger area than the picture displayed at any one time, the generating means incorporating means for alterin...

A safety system for overhead hoisting cranes is provided which incorporates a overload release coupling in the high speed drive shaft between the prime mover and the gear reducers driving one or more hoist drums with a dual reeving and a safety brake acting on the high speed drive shaft at the gear reducers and controlled by an overrunning clutch and a control means.

Water-based explosives that use siliceous boron-containing microspheres as sensitizing agents are stabilized by adding multivalent metal ions to the explosives. Zinc salts are especially useful.