Mitel Corporation

John A Cribb

Robert A Durance

Graham A Neathway

John R Whitbread

A call denial apparatus for identifying a telephone subscriber's line out of a group, whereby access to a trunk is denied in the event the subscriber dials one or a group of predetermined digits. A subscriber not to be denied access to the trunk is identified by applying a tracer signal to the seized trunk and the tracer signal on one of the group of subscribers' lines is detected. Accordingly specially modified telephone sets and lines are not required.

Telephone call denial system

A junctor checking system for an electronic PABX which checks the potential of the junctor under control of a microprocessor. A voltage level sensing circuit is connected to the junctor to be checked; a resistor connects the input of the voltage level sensing circuit to a voltage source. In the event the impedance of the junctor to ground is not as expected with respect to at least one threshold, the junctor is considered faulty and a different idle junctor is selected.

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Ottawa, Canada

John A Cribb