Abstract: Circuitry for integrity verification is provided to prevent a calling party from unknowingly remaining connected to a faulty trunk connection between an automatic switching office and an operator-assisted office. New circuit arrangements are added to the outgoing trunk circuit of the automatic office and to the line circuit of the operator-assisted office. At the outgoing trunk circuit, binary memory elements and associated circuitry are employed to delay the completion of the normally executed cross-office continuity check at the automatic office, thereby delaying release of common control equipment at that office. During the delay interval, interoffice integrity check signals are exchanged between the outgoing trunk circuit and the line circuit. Circuitry is added to the line circuit for the generation of a wink signal in response to a seizure signal from the outgoing trunk circuit. This wink signal is received at the trunk circuit as a timed off-hook signal followed by a steady on-hook signal.