A merchandise security system in which a signal having a first frequency is generated and is multiplied or divided by n to provide a signal having a second frequency which is transmitted. A responder circuit in a tag on the merchandise divides or multiplies the transmitted signal by n and transmits it to a receiver where it is compared with the originally generated first frequency and is used to produce an alarm signal.

A detector device adapted to be used for detecting coins and other metal objects for various purposes including to distinguish between genuine and non-genuine or counterfeit coins, the subject detector device includes an electric tank circuit having a coil through which, or adjacent to which, an object or coin to be detected moves, apparatus to electrically shock the tank circuit to produce an output representative of the object or coin and represented as a damped wave signal the frequency and s...

A system for monitoring the position of a receptor reradiator in a surveillance zone having a first means for transmitting a first signal through the zone, and a receptor reradiator operable in response to reception of said signal to radiate at least one reply signal which is a function of the first signal and of the position of said receptor reradiator in the zone. There is also a receiver for receiving the reply signal, means controlled by the receiver, dependent upon the reply signal to indic...

A method and apparatus for detecting sand particles in a flowing fluid, for example, the production from a gas or oil well. An acoustic transducer is used to detect the sand particles and the resulting signal is filtered to pass a frequency band of 50 to 500 kiloherz. A pulse height discriminating means and pulse counter is provided for counting the number of pulses that exceed a pre-set amplitude.

Estrogen receptor protein, estrophilin, in a tissue sample is detected and quantified by radiochemical methods involving selective binding of the protein to controlled pore glass beads. Also disclosed are methods for selectively removing undesirable degradation products from radiochemically labelled non-polar steroid reagents, especially estradiol.

In a method of detecting sheets which do not have a genuine watermark (i.e. watermarks which result from variations in fibre distribution introduced during manufacture) the absorption of ultra-violet radiation is measured for each sheet in the area in which the watermark is expected to be present, and the transmittance of light by this area of the sheet is also measured. Sheets for which the absorption measurement does not show a substantially constant value, and sheets for which the light-trans...

A test substrate, including a semi-permeable membrane which retains bacteria on the membrane and which has a net positive surface charge to permit coloring of bacteria thereon with a cationic dye, without the membrane adsorbing substantial amounts of said dye. Substrate is included in a kit for detecting bacteria.

A simple and inexpensive direct current voltage level detector is shown which has a significant immunity against interfering alternating current signal components. The output of a standard analog threshold detector is successively sampled by clock pulses having twice the repetition rate of the frequency of the expected interfering alternating current components. By requiring two successive samples to be above the threshold of detection, immunity is provided against false detection due to tempora...

A process is provided for measuring the water and sediment content of a wet stream which is predominantly non-aqueous. The process requires removing a sample of the wet stream, extracting a dry stream sample from the wet stream sample, and comparing the dielectric constants of the wet and dry streams. Leakage of any of the wet stream sample into the dry stream sample will adversely affect the comparison of dielectric constants. Accordingly, periodically the apparatus used for the process is chec...

Apparatus and method for detecting and measuring chloride ion and therefore dissociable chlorine compounds using a solid electrolyte concentration cell. Applicable only to gaseous samples.