Abstract: A battery charging aparatus and method are provided for charging a battery using current control with a switching power supply charging circuit coupled to the battery. During a first charging phase, a predetermined constant charging current is applied to the battery. The battery voltage is monitored and a second charging phase is started when the battery voltage reaches a predetermined threshold voltage. During a second charging phase, a sequence of stepwise decreasing-amplitude current pulses are applied to the battery. The envelope for the decreasing current pulses is exponential which is characteristic of the current for voltage controlled charging methods. The battery voltage is maintained at a temperature compensated target with a 1% tolerance. The charging current is compared to a predetermined minimum amplitude value and a third charging phase is started when the sequential charging current pulse equals the predetermined minimum amplitude value.

Abstract: Control information for a flexible magnetic disk storage assembly is recorded on the periphery of the disk in a region not used for recording data. The control information is read through the protective cover or envelope which encloses the disk by means of a magnetic transducer such as a four track audio cassette head which bears against the envelope. By recording index and sector pulses as part of the control information, hard sectoring can be inexpensively and accurately achieved. A recorded fixed frequency control signal can be read and used as part of the feedback loop in a phase locked oscillator used to control a d.c. motor driving the spindle. The control information can also include servo tracks which assist in registering the data transducer directly over data tracks on media which has changed its dimensions.

Abstract: A single gap transducer simultaneously senses recorded control or servo signals and records data signals. A magnetic medium used with this invention is preferably a single coating magnetic medium. During recording, the recording signal is appropriately subtracted from the readback signal for removing write signal effects on the readback signal. The servo signals are preferably deeply recorded into the magnetic coating whereas the data signals are preferably recorded in an outer surface portion of the magnetic coating.

Abstract: Stepper motor control circuitry including a phase locked loop circuit formed by a phase detector outputted to a filter and a voltage controlled triangular and square wave generator which has a frequency control input terminal connected to the output of the filter and which provides a square wave on an output thereof connected as an input to the phase detector. An oscillator drives the phase detector, and the outputs of the generator are connected as inputs to a pulse width modulated driver which has its outputs connected to the coils of the stepper motor. A differential amplifier is connected across one of the coils of the motor, and a balanced modulator synchronous detector or multiplier has two inputs one of which constitutes an output of the differential amplifier and the other of which is a connection to the square wave output of the generator.

Abstract: Disclosed is a circuit board and a process for the manufacture thereof providing a circuit board comprising a metal core having parallel first and second major faces and exhibiting high thermal and electrical conductivity. The circuit board includes electrical insulating layers of thermally conductive, dielectric material applied to the first and second major faces of the metal core. Protecting the dielectric layer and copper conductors is a solder mask layer applied to the dielectric layers and forming outward facing major surfaces. A plurality of insulated and grounded vias having electrically conductive interior rings connecting the major surfaces are provided through the board. Conductive sleeves within the vias are either electrically insulated from the metal core by dielectric material or in electrical contact to the metal core for grounding.