Abstract: A gravure printing press with an electrostatic assist unit having a fault detection circuit and crowbar circuit in which the crowbar circuit has a transformer with a primary winding and a plurality of secondary windings. Each of the secondary windings has a field-effect transistor which is turned on in response to the detection of a fault condition whereby the voltage applied to the press is substantially reduced to zero and any electrostatic charge is substantially removed. A capacitor is coupled in parallel with the gate and source terminals of each field-effect transistor to lengthen the on-time of the transistors.

Abstract: A method for conducting a proofing operation of a rotogravure printing cylinder includes preparation of a steel drum having in sequence from the outer steel surface a layer of plastic such as Mylar.RTM., a blanket consisting of a rubber composite material, a paper/foil layer with the foil side facing outwardly, and a proofing sheet consisting of normal printing paper. The rotogravure cylinder which is to be proofed is brought into contact with the thus-prepared drum, and a high voltage is applied to the foil via the proofing sheet. The rotogravure cylinder is inked and rotated through one printing revolution so that a complete impression is made on the proofing sheet. The high voltage assists in the transfer of ink from the cups of the rotogravure cylinder to the proofing sheet. The impression produced by the rotogravure cylinder can then be checked before the rotogravure cylinder is sent to a user.

Abstract: A high-voltage crowbar circuit continually senses the load impedance and crowbars the output voltage applied to a load if the load impedance falls below a selected value. A differentiator circuit at the load senses variations in load voltage and can trigger the crowbar operation if the voltage variation as a function of time exceeds a preselected load.

Abstract: An emergency lighting system including an inverter for operating a fluorescent lamp from a battery upon failure of the primary AC voltage source. A transformer connected to the AC source is provided with a single secondary winding for providing both current for charging the battery and a voltage proportional to the AC voltage to circuit inhibit means for allowing inverter operation when AC voltage falls below a predetermined level.