1977-02-28
1978-06-13
Cooper, William C.
H04M 166
Patent
active
040950565
ABSTRACT:
A toll restrictor access circuit for use with a plurality of toll restrictors shared by a group of telephone lines is disclosed. The access circuit connects a toll restrictor to a telephone line when a call is initiated so that the number dialed by the caller can be monitored to determine whether the number being dialed is one that is authorized. The toll restrictor controls a polarity reversal relay in the access circuit to disable the telephone dial until a dial tone is detected. If the caller dials a valid number, the toll restrictor energizes a permit relay in the access circuit which allows the call to be completed in the normal manner. The permit relay also de-energizes the polarity reversal relay thereby disabling the telephone dial and releases the toll restrictor so that it may be used by another telephone line. If on the other hand the caller dials a prohibited number, the toll restrictor energizes a restrict relay which disconnects the telephone instrument from the telephone line. At this point, either a busy signal or a recorded announcement can be connected to the telephone instrument. Energization of the restrict relay also de-energizes the polarity reversal relay and releases the toll restrictor. Connection of the toll restrictor to the telephone line also results in energization of a supervisory relay which, together with a time delay circuit, is effective to defeat unauthorized calls by means of flashing the telephone instrument hook switch. The access circuit permits the use of two or more toll restrictors to be shared by a group of telephone lines and may be used either with key system or switchboard system installations. In either type of installation, restricted and non-restricted telephones are classified upon installation. The access circuit includes circuitry to recognize the classification of the telephone instruments.
REFERENCES:
patent: 3331926 (1967-07-01), Largey
patent: 3784757 (1974-01-01), Woolf et al.
patent: 3872260 (1975-03-01), Oatis
patent: 3902024 (1975-08-01), Hijikata et al.
Cooper William C.
Tele-Path Industries, Inc.
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