Abstract: A magnetic coil, especially for use as an r.f. transmit/receive coil in NMR apparatus, comprises a continuous closed conductive loop would round a former 1. A pair of external terminals 2 and 3 both lie in a plane 4 constituting a plane of symmetry and the coil is would so that there is mirror symmetry about this plane. There are two electrically parallel paths between terminals 2 and 3 each restricted to one side of the plane of symmetry 4 and the resultant magnetic field when a potential difference is applied between terminals 2 and 3 is such that equal magnetic fields are produced on both sides of the plane of symmetry 4.

Abstract: A set of NMR free induction signals generated in nuclei in a sample are recorded in the presence of a magnetic field gradient to a static magnetic field in which the sample is positioned. Prior to recording a magnetic field gradient orthogonal to the said gradient is applied to phase-encode the signals. The individual signals of a set are differentiated by being recorded after different time integrals of the phase encoding gradient. The magnitudes of successive time integrals have a non-monotonic relationship with each other so that sufficient signal data is recorded to enable the Fourier transform operation to commence before half or less of the set of signals has been recorded. Preferably the relationship between the magnitudes of successive time integrals corresponds to a numerical sequence represented by a monotonic sequence of binary numbers re-arranged in bit-reversed order.

Abstract: Ultrasonic phased array method and apparatus for the static or dynamic investigation of structures, such as organs of the body, or intra-uterine detail, wherein ultrasonic echo pulses, reflected back from a testpiece to one or a group of adjacent transducers of a linear transducer array, are converted to corresponding electric signals which are then processed to maximize the response to the echo pulses reflected from points on a predetermined axis and to minimize the response to all other echo pulses. The method is repeated using another group of transducers in the array and another predetermined axis to produce fields of video information which are focussed and then interlaced to provide an image of the testpiece at a particular instance, the method steps being repeated in rapid succession to provide a video image representative of the testpiece in real time.