Abstract: Interface for a silver recovery unit (11) for indicating the operating condition of at least one pump (9a, 9b). A sensor (10) for detection of the operating condition of the pump (9a, 9b) is installed outside the at least one pump (9a, 9b) such that during installation an intervention in the electronic unit (24) of the pump (9a, 9b) or in the pump (9a, 9b) itself is avoidable. The output signal of the sensor (10) is passed to a series-connected electronic circuit (400) that comprises a series connection of an amplifying means (40), a first filtering means (41), a rectifying means (42), a second filtering means (43) and a comparator (44).

Abstract: An interior drum type printer includes a paper feed mechanism permitting quick and simple paper advance to a printing position. This is attained in that a print head is connected to a paper feed means which is mounted for controlled rotation together with the print head about a shaft arranged within the printing drum.