An inexpensive and easily constructed circuit is described which provides fail‐safe automatic venting of turbomolecular pumps regardless of the power shutdown mode. Using Pfeiffer TCF 101 vent control unit, shutdown of the turbomolecular pump will occur with automatic delayed pump venting initiated by a power failure, and with manual venting. This paper describes a circuit modification to add an additional mode, automatic delayed pump venting activated from the front panel on/off switch, to the vent control unit. The circuit requires no additional power supplies and mounts in existing space in the control unit.

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