Abstract: A pressure responsive check valve designed to quickly close in response to a drop in pressure below a pre-determined level. When used at the top of a fluid filled tank such as one used for heating oil, the valve prevents tank syphon by stopping fluid flow at the tank in the case of breakage of supply or return lines, The valve is contained in a pre-assembled unit for ease of installation.

Abstract: In a printer in which drive transistors coupled to hammer drive coils control energization of the coils within each of a plurality of magnetic print hammer actuators to provide firing of hammer springs associated with the print hammer actuators, leakage of one or more of the drive transistors when they are switched off is detected by a testing circuit which flags a fault condition to turn off the driver circuits if the current at a junction common to all of the drive transistors exceeds a predetermined threshold value. This provides an early warning system in which faulty transistors are routinely detected well before they have a chance to fail and thereafter burn out the associated coil included within a hammerbank of the printer.

Abstract: A printer system having local control for dynamically positioning a print head relative to a print medium utilizing positioning and print data signal inputs, including a control unit for receiving and storing data inputs, the control unit including circuit means responsive to the positioning data for arranging and outputing the stored print data to a print head, control circuitry connected to said control unit and head positioning apparatus employing a movable print medium connected to the control circuitry for positioning the head in relationship to the web in response to said control circuitry so that the head is thereby dynamically controlled by the respective data signal inputs.