Facsimile and static presentation processing – Facsimile – Facsimile system interface
Patent
1995-08-09
1998-04-07
Lee, Thomas D.
Facsimile and static presentation processing
Facsimile
Facsimile system interface
358407, H04N 100, H04N 132
Patent
active
057370940
ABSTRACT:
An secured fax adapter apparatus uses a relay circuit to selectively couple a G3 fax to a secured line via a secured telephone unit (STU). The G3 fax can alternatively be coupled to a public switched telephone network (PSTN) via a PSTN port. The secured fax adapter has an enhanced DAA having a controller, a fax communication circuit, a current limited off hook detection circuit, a relay circuit for selectively coupling the external device ports, and a ring generation circuit for producing a square wave for ring generation. In one embodiment, the current-limited off-hook detection circuit uses a symmetrical network of transistors coupled to diodes to limit the current drawn by a load. In another embodiment, the relay circuit has four relays for selectively coupling the G3 fax to the fax communication circuit, the STU to the PSTN, the G3 fax to the PSTN, or the STU to the fax communication circuit. The relay circuit has an additional relay for coupling the off-hook detection circuit to the fax communication circuit.
REFERENCES:
patent: 4991200 (1991-02-01), Lin
patent: 5333190 (1994-07-01), Eyster
patent: 5499287 (1996-03-01), Campbell
patent: 5546451 (1996-08-01), Shen
patent: 5563938 (1996-10-01), Soshea et al.
Grant II Jerome
Lee Thomas D.
Ricoh & Company, Ltd.
Ricoh Corporation
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