1984-04-25
1985-10-08
Rubinson, Gene Z.
179 2C, 179 2DP, H04M 1100
Patent
active
045462135
ABSTRACT:
A modem security access circuit device, which is coupled between a dial-up telephone line and an automatic-answering modem, includes a line matching transformer circuit which trips an incoming ringing signal for a predetermined time interval. During the predetermined interval the caller, who receives no indication of the presence of the modem, must send an access code consisting of a preselected sequence of up to ten digits from a DTMF tone pad, or else the line matching transformer circuit disconnects from the telephone line. The device also includes a decoding circuit coupled to the line matching transformer circuit for receiving the access code. If the correct access code is received, the decoding circuit activates a ring supply generator which provides an internal ring signal to activate the modem. The activated modem is then coupled to the telephone line through the line matching transformer circuit and a carrier signal is sent to the caller. In addition, the device includes a lock-out circuit which disables the decoding circuit for a preselected time interval if the caller sends a predetermined number of invalid digits. Furthermore, the device includes a counter circuit for counting the number of invalid digits received and an LED display for visual read-out of the invalid digit count.
REFERENCES:
patent: 3902016 (1975-08-01), Blouch
patent: 3984637 (1976-10-01), Caudill et al.
patent: 4430728 (1984-02-01), Beitel et al.
Brady W. J.
Rubinson Gene Z.
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