Abstract: For the identification of macro-organisms, especially fish, visible implant tags having identification codes of fluorescent colorants are implanted into at least partially transparent tissue of the macro-organisms such that the visible implant tags are visible. The encoded information is obtained from the tags by measuring the spectrum of light emitted by the fluorescent colorants. The tagged fish need not be captured to read the tags. The information may be obtained through a significant depth of medium and also independently of the size of the tag or its orientation. Florescent dyes or, more preferably, fluorescent pigments may be used for the identification codes.

Abstract: An undersea probe which can be attached to marine animals for collecting data as to light intensity and temperature in regions where the marine animals travel. The probe is essentially omnidirectional in its light acceptance capability so that light intensity measurements will not be dependent upon any particular orientation of the probe. The probe includes a central optical fiber containing a fluorescent dye enclosed in a transparent or translucent, protective and fouling-resistant sheath. The optical fiber is provided at its outer end with a fiber terminator which blocks entry of light into the end of the fiber. At its opposite inner end, the fiber is coupled to a light detector in a housing which may be implanted in the marine animal. The optical fiber exhibits radial changes in its refractive index to trap light which approaches the surface of the fiber from inside and which makes a small enough angle with that surface. Such light is propagated along the fiber to the light detector.

Abstract: An apparatus detects a magnetic tag implanted in an organism as detector is moved past the organism by detecting a magnetic field difference between two positions. Prior to examination of a specimen under test, the outputs of a plurality of loops detecting magnetic fields are balanced in a uniform magnetic field. As a consequence, when one of the coils is exposed to a different magnetic field than the other of the coils this difference is detected and an alarm is sounded to indicate that the magnetic tag has been detected.

Abstract: In a method for tagging members of a large group of macro-organisms so that each macro-organism is assigned to a respective subgroup, successive segments of wire are cut from a continuous length of wire. During implantation, a tag is ejected and stored to define the beginning of a set of successive tags corresponding to a subgroup of macro-organisms. The tags of that subgroup are then severed from the length of wire and implanted into respective members of the particular subgroup. Subsequently, another tag is severed from the wire and stored to mark the end of the subgroup. Upon capture of a member of a subgroup, the tag is excised, the respective multidigit code is read and compared with the multidigit codes of the stored tags to determine to which subgroup the captured macro-organism belongs.

Abstract: A fishing net includes a cord having a multiplicity of strands including an identification strand marked at spaced intervals with sequential numerical codes. The preselected strand is substantially inextricably incorporated in the cord so that the preselected strand extends along the length thereof. The cord is in turn incorporated in the net so that the cord extends substantially from one end of the net to an opposite thereof. The cord has ends located at readily accessible preselected points relative to the net so that a smallest numerical code and a largest numerical code on the cord are easily determinable upon visual inspection of the net.

Abstract: A photon detector includes a semiconductor device, such as a Schottky barrier diode, which has an avalanche breakdown characteristic. The diode is cooled to cryogenic temperatures to eliminate thermally generated charge carriers from the device. The diode is then biased to a voltage level exceeding the avalanche breakdown threshold level such that, upon receipt of a photon, avalanche breakdown occurs. This breakdown is detected by appropriate circuitry which thereafter reduces the diode bias potential to a level below the avalanche breakdown threshold level to terminate the avalanche condition. Subsequently, the bias potential is reapplied to the diode in preparation for detection of a subsequently received photon.

Abstract: Method and apparatus for measuring the repetition rate of a series of electrical input pulses. An electrical quantity having a predetermined initial value changes at a predetermined rate in response to the presence of an input pulse; a later value of the quantity is detected in response to the presence of the next input pulse; and, in response to the later value of the quantity, an electrical output signal is provided that is indicative of the repetition rate of the input pulses. Typically the steps are repeated for a plurality of successive input pulses and a control signal maintains the detected later values of the quantity substantially equal to a predetermined comparison value. An alarm may be provided in response to any substantial change in the repetition rate of the input pulses.