Abstract: A signal structure for high speed data communication selects each signal point in the structure to attain a low probability of error in the presence of both additive noise and multiplicative noise. Transmission apparatus for practice of the invention employs an encoder which responds to digital data to produce a QAM signal having parameters selected according to the new signal structure, and receiving apparatus employs a decoder which converts a received QAM signal to digital values according to the same structure.

Abstract: A signal structure for high speed Trellis coded data communications selects each signal point in the structure to attain a low probability of error in the presence of both additive noise and multiplicative noise. Viterbi decoding is modified to take account of the multiplicative noise energy content of the received signal.

Abstract: A network control and test system for application to data communications networks. In a first mode of operation, the system learns the network configuration automatically and builds a table describing the network configuration. In a second mode of operation, the system automatically monitors the status of the network and each of its component units, periodically polling the network for changes of status and updating the information in the network configuration table to reflect such changes. In a third mode of operation, selective sites in the network may be tested under control of the system at previously selected and entered times of day, at which times previously chosen tests are performed without the need for operator intervention. In a fourth mode, an operator can manually command the system to perform certain tests and control functions.

Abstract: A network control and test system for application to data communications networks. In a first mode of operation, the system learns the network configuration automatically and builds a table describing the network configuration. In a second mode of operation, the system automatically monitors the status of the network and each of its component units, periodically polling the network for changes of status and updating the information in the network configuration table to reflect such changes. In a third mode of operation, selective sites in the network may be tested under control of the system at previously selected and entered times of day, at which times previously chosen tests are performed without the need for operator intervention. In a fourth mode, an operator can manually command the system to perform certain tests and control functions.

Abstract: An improved ring core second harmonic flux gate magnetometer is constructed as a module for use as a ferrous metal detector. Pairs of modules may also be used as gradiometers. Various uses and winding arrangements on the ring cores are disclosed.

Abstract: A passive ferromagnetic detection station in which the position of the ferromagnetic object carried by a person may be indicated. A plurality of gradiometers mounted at predetermined vertical positions along two vertical members are used to sense any disturbances in the earth's magnetic field. Each gradiometer has a predetermined pattern or area of sensitivity to magnetic fields in which it senses disturbances in the earth's magnetic field. In a preferred embodiment the sensitivity patterns may overlap in predetermined areas. The outputs of the gradiometers are individually processed and converted to digital signals. The digital signals may be used to control a visual display device.