Abstract: The hangup apparatus uses an inadvertent off-hook detector circuit designed to detect the off-hook "howler" alert signal transmitted to a telephone by the telephone company when the telephone has been off-hook for a period of time without any user activity. The detector circuit provides an automatic hangup signal to an automatically actuated hangup switch, disconnecting the telephone voice network from the telephone lines and restoring service to the telephone. One version of the invention can be incorporated into newly manufactured telephones, and another is suitable for use with existing telephones. Both versions can be realized using readily available commercial electronic components.