Abstract: The laser beam level instrument includes a laser diode mounted on a pendulous platform suspended from a frame by gold plated Mylar strips which also serve as conductors for supplying power to the diode. The strips are mounted with a 180 degree twist to overcome resistance to flexing/bending so that the platform moves freely under the influence of gravity to provide automatic self-leveling. The diode operates on low d.c. voltage but if d.c. is applied to the strips the magnetic field around the Mylar strips will have sufficient force relative to the geomagnetic field to interfere with free pendulation. So 4.5 volts d.c. is stepped up and inverted to about 20 volts a.c. to avoid interference with the geomagnetic field and to reduce power loss across the gold plated strips. The a.c. voltage is then stepped down and converted back to d.c. voltage (2-3 volts) on the platform to power the diode.

Abstract: A voltage control circuit for an uninterruptible power supply (UPS), said UPS involving a controlled rectifier operating from an input AC line to charge batteries and to hold them at a constant voltage; the batteries supply power to an inverter which in turn produces an AC output, such output being uniquely controlled by efficiently and accurately compensating for any fluctuations due to battery voltage changes or to load changes.

Abstract: A constant voltage, constant frequency, uninterruptible a.c. power supply having a line voltage regulator, a rectifier-inverter with an emergency battery power supply and a transfer switch for selectively connecting the line voltage regulator and rectifier-inverter to a load. Under normal conditions, the line voltage regulator and rectifier inverter derive their operating power from the power line and are both connected to the load. If the fault detection system detects a power line fault, it causes the transfer switch to disconnect the line voltage regulator from the load and the rectifier-inverter supplies power to the load from the emergency battery power supply. If the fault detection system detects a rectifier-inverter fault, it causes the transfer switch to disconnect the rectifier-inverter from the load. A synchronization control system regulates the phase of the rectifier-inverter.

Abstract: A line isolation monitor for detecting faults of lines isolated from ground in which a constant current generator generates an electrical signal having one or more frequencies near the power line frequency and applies the electrical signal to the power lines. A signal sensor detects the generated electrical signal on the power line and a discriminator determines the effect of the phase angle of the impedance from each of the power lines conductors to ground and the effect of the relative magnitudes of each of the conductors impedance to ground to detect a fault. A threshold circuit generates an alarm signal if the current flow is above a predetermined level, to energize audible and visible alarms.

Abstract: An electrical system wherein an electrical condition such as voltage is regulated by means of a static regulator of the ferroresonant type, including a high reactance transformer and wherein the regulator is particularly stable during start-up and under transient conditions by use of a clipping ballast load.