Abstract: The illumination intensity of a fluorescent lamp which has cathodes and an ionizable medium separating the cathodes is controlled by a method in which the lamp is ignited once during each half-cycle of applied AC current and is thereafter extinguished during that same half-cycle. The lamp is ignited by creating and applying an ignition voltage pulse of a magnitude greater than a characteristic operating voltage of the ionizable medium between the lamp cathodes. The lamp is extinguished by reducing the voltage between the cathodes to a value less than the operating voltage, at a point prior to a zero crossing of the applied AC current half-cycle in which the lamp was illuminated. Because the extinguishing point occurs prior to the end of the applied AC current half-cycle, the illumination intensity is reduced during each half cycle. The characteristics of the ignition pulse reliably ignite the lamp, thereby allowing extinguishing control on a half-cycle by half-cycle basis.

Abstract: The illumination intensity of a fluorescent lamp is controlled in response to control signals generated at a remote location on the power supply conductors of a lamp circuit and decoding those control signals at the fluorescent lamp to control the illumination intensity. A dimming controller is connected in the lamp circuit remote from the lamp and generates first and second control signals indicative of a request to increase or decrease, respectively, the lamp illumination intensity. The control module is connected in the lamp circuit to fluorescent lamp and the control module receives the control signals. The control module continually increases and decreases the illumination intensity of the lamp in response to the first and second control signals, respectively. The illumination intensity is controlled by adjusting a time point within each half-cycle of applied power where the lamp is extinguished.

Abstract: The cathodes of a fluorescent lamp are preheating and the medium between the cathodes is ignited into a plasma by heating the cathodes for a predetermined warm-up time period by conducting current from a supply power source through the cathodes for a conductive time interval, and applying a relatively high voltage starting pulse to the cathodes at the end of the conductive time interval or alternatively suppressing the high voltage starting pulse during the predetermined warm-up time period. Suppressing the high voltage starting pulse during the warm-up time period, thereby preventing erosion the thermionic coating of the cathodes due to positive ion bombardment. A controllable semiconductor switch is connected to the cathodes to control the current flow through them. The high voltage starting pulse is derived from commutating the semiconductor switch into a nonconductive state when the applied current level drops to the characteristic holding current value of the switch.

Abstract: A voltage-boosting and current-regulating circuit delivers energy from a high voltage resonant circuit source to a fluorescent lamp. A controllable switch is connected in series with the lamp cathodes and is triggered into conduction during a predetermined conductive time interval within each half-cycle of current conducted through the plasma from the resonant circuit. A charging current which flows during the conductive time interval stores energy in the resonant circuit which is subsequently released as a boosted voltage and as increased current flow through the plasma. The boosted voltage allows higher efficiency illumination lamps to the used, and regulation of the conductive time interval achieves the optimal current conduction through the lamp.

Abstract: A control module and method controls the operation of a fluorescent lamp in a circuit in which the lamp is connected to a ballast and energized by alternating half-cycles of power supplied from an AC power source. The fluorescent lamp has cathodes and a medium which emits light energy when energized into a plasma. A controllable switch conducts half-cycles of AC current through the cathodes and commutates into a non-conductive condition. A sensor supplies sensing signals related to an electrical condition at the cathodes. A state transition controller controls the switch. The state transition controller establishes a power-up, warm-up, ignition and fire operational states and transitions between the states in response to the electrical condition sensed and the time duration of those conditions. The lamp lights more reliably, premature failure of the ballast and cathodes is prevented due to overheating, and the lamp is controlled effectively by input signals in the form of short power interruptions.

Abstract: A method of regulating an operating current conducted from a source through a fluorescent lamp involves conducting a charging current from the source through an energy storage element of a resonator circuit to store a predetermined different degree of energy in the element than is stored by conduction of the operating current, and then releasing the stored energy to regulate the operating current delivered to the plasma within the lamp. The conductive time interval during which charging current flows is adjusted to regulate the lamp current to an optimal level for the best illumination efficiency from the lamp and the longest useful lifetime of the lamp. The conductive time interval is adjusted based on the voltage across the plasma. The known negative impedance characteristics of the plasma correlate the sensed voltage to the lamp current conducted by the plasma, thereby allowing regulation of the lamp current to the desired optimal level.

Abstract: A starter for a fluorescent lamp selectively conducts current from an AC power source through a ballast and cathodes of the lamp during one half cycle of conducted current from the AC power source. Thereafter and during the same on half cycle of current the starter ceases conducting current substantially instantaneously when the current is of a predetermined level. The resulting di/dt generates a starting voltage pulse from the ballast sufficient to ignite the plasma. The starting pulse occurs when the AC voltage across the cathodes exceeds an ignition voltage of the plasma. Preferably the starter employs a thyristor which has a predetermined holding current at least equal to the predetermined level to allow the inherent commutation of the thyristor to create the di/dt. The current conducted by the thyristor heats the cathodes prior to igniting the plasma.

Abstract: A control module controls the illumination intensity of a fluorescent lamp. A controller controls a switch to conduct current through cathodes of the lamp, and the switch ceases conducting current when commutated into non-conduction. The switch is triggered into conduction at a predetermined extinguishing point within and prior to the end of each half-cycle of applied AC current. The switch is thereafter commutated into non-conduction at a predetermined ignition point when the applied AC current reaches a predetermined level near the zero crossing point of each half-cycle of applied AC current. The current level at commutation creates a sufficiently high di/dt effect to cause an ignition pulse of voltage from the ballast across the lamp cathodes sufficient to ignite the ionized medium into an illumination plasma. The switch extinguishes the plasma. The illumination intensity of the lamp is related to the time between the ignition point and the extinguishing point.

Abstract: A stability indicator for a marine vessel. The indicator continuously determines a GM value for the vessel equal to the square of the vessel's beam length times the square of the vessel's rolling constant divided by the square of the vessel's rolling period. The rolling period is determined by means of a gravity sensor whose output is an electrical signal corresponding to the instantaneous magnitude and direction of the roll angle. Electronic level adjustment and gain selection means are also provided, to compensate for the fact that the stability indicator may often be installed with the gravity sensor off-horizontal. The signal from the gravity sensor is input into a data processor that computes the rolling period by first analyzing the roll angle signal to establish a zero level and threshold levels above and below the zero level.

Abstract: A remote control system capable of utilizing manually encoded signals is disclosed. The system is particularly suitable for use in the logging industry because it is capable of utilizing standardized whistle signals for both remove control and audible signalling purposes. The system includes a transmitter for transmitting a manually encoded signal. The control signal is received by a receiver and is decoded by a decoder that reduces the manually encoded signal to a digitized signal. The digitized signal is compared with a set of reference digitized signals, and if a match is found, a corresponding output control signal is applied to a controlled device such as a yarder.

Abstract: An improved decoder for providing a decoder output signal when a tone signal contains frequencies that are sequentially within a predetermined passband surrounding first and second detection frequencies f.sub.1, f.sub.2. A tone signal is mixed with a reference signal which alternates, at a multiplex frequency, between sine and cosine signals, each being at a predetermined reference frequency which is less than the multiplex frequency. A tone switching logic circuit normally maintains the reference frequency at a value substantially equal to the frequency f.sub.1. The mixed signal is coupled through a demultiplexer to respective inputs of first, second, third and fourth low pass filters, each of which has a cut-off frequency which is one-half of the decoder passband. The respective outputs of the filters are coupled through a multiplexer to a squarer.