Abstract: In order to provide a dependable check on the reliable functioning of contacts of switches or relays which control a control device, to ascertain whether they occupy the desired rest contact position and/or have a sufficiently high mains voltage, the rest contacts of the two switches can be connected in parallel by way of a respective electrical resistor to a pole of the voltage source and both resistors can be connected in series to a charging capacitor which, upon the attainment of a given electrical charge or voltage (threshold voltage) activates the control device and in particular feeds a threshold switch or itself serves as such.

Abstract: An automatic furnace comprises an actuator for an electric igniter. The electric igniter has a distinctly lower standard voltage, e.g., 120 V, than the network voltage, e.g., 230 V and is operated by the network voltage. The network voltage is fed into the power regulator before the igniter. The power regulator clocks the network voltage with an adjustable keying ratio, so that only part of the full wave trains of the network voltage becomes active at the electric igniter. In an advantageous embodiment, the keying ratio is variegated by the actual level of the network voltage.