Abstract: A method of monitoring an electrical system may include providing a ground fault detection unit, operating a transformer rectifier unit to provide DC power to a load, sensing, via a current sensor, a ground current at or about an output of the transformer rectifier, and/or monitoring a sensor output from the current sensor via the ground fault detection circuit. The ground fault detection circuit may be configured to detect ground faults at frequencies of at least 30 kHz.

Abstract: An electrical system includes a ground fault detection unit including a low frequency ground fault detection circuit and a high frequency ground fault detection circuit, and/or a ground fault control unit connected to the low frequency ground fault detection circuit and the high frequency ground fault detection circuit. The ground fault unit may be configured to detect a ground fault according to an output of the low frequency ground fault detection circuit and/or an output of the high frequency ground fault detection circuit. The electrical system may include a first current sensor connected to the low frequency ground fault detection circuit and/or a second current sensor connected to the high frequency ground fault detection circuit.

Abstract: An electrical system includes a ground fault detection unit including a low frequency ground fault detection circuit and a high frequency ground fault detection circuit, and/or a ground fault control unit connected to the low frequency ground fault detection circuit and the high frequency ground fault detection circuit. The ground fault unit may be configured to detect a ground fault according to an output of the low frequency ground fault detection circuit and/or an output of the high frequency ground fault detection circuit. The electrical system may include a first current sensor connected to the low frequency ground fault detection circuit and/or a second current sensor connected to the high frequency ground fault detection circuit.

Abstract: A method of monitoring an electrical system may include providing a ground fault detection unit, operating a transformer rectifier unit to provide DC power to a load, sensing, via a current sensor, a ground current at or about an output of the transformer rectifier, and/or monitoring a sensor output from the current sensor via the ground fault detection circuit. The ground fault detection circuit may be configured to detect ground faults at frequencies of at least 30 kHz.

Abstract: A biometric network for use in time and attendance applications is disclosed. The system includes at least one biometric device which is capable of identifying a user and generating data related to the user. The biometric device compares live biometric data, for example, fingerprint data, with stored biometric data, such as on an optical data card, memory card, smart card, or other biometric storage device. The invention includes a central data center which communicates with the biometric devices and receives the generated data transmitted from the biometric devices. The devices may be connected to the central data center via serial connection, wireless connection, modem, ethernet or the Internet. The generated data may relate to the attendance of the user at a particular location, the timing of particular events, such as entrance and exiting time, check-in times, or other time-stamp requirements.