Abstract: A single cycle control system for a press or the like in which interrupted stroke protection is combined with novel interconnections of the control components in the system such that the failure of any single control component cannot endanger the operator of the machine. Relay failure (even a simultaneous failure of two) is completely eliminated as a possible source of an unexpected repeat stroke of the machine. The solenoids for operating the air valves that control the operation of the machine are energized initially through the usual run switches for the machine, after which these solenoids are kept energized through separate holding circuits which include limit switches operated by the machine and switches operated by the respective air valves.

Abstract: An SCR motor speed controller in a forced air heating and/or cooling system has a relay-operated potentiometer with a variable voltage tap which controls the speed of the fan motor in accordance with the total demand from individual room thermostats. Each room thermostat controls the operation of a corresponding control relay to short-circuit a corresponding part of the potentiometer on one side of its variable-voltage tap and to add in a corresponding part of the potentiometer on the opposite side of its variable voltage tap in response to a demand from the thermostat.