Earl K Martin

US Patent:

43307442, May 18, 1982

Filed:

Dec 16, 1980

Appl. No.:

6/216927

Inventors:

Milton L. Embree - Reading PA
Earl O. Martin - Temple PA

Assignee:

Bell Telephone Laboratories, Incorporated - Murray Hill NJ

International Classification:

G05F 320

US Classification:

323316

Abstract:

The subject circuit is a converter/isolation circuit which employs only a few components yet functions to monitor a particular signal and produce an output signal which is identical to or proportional to (to a high degree of accuracy) to the monitored input signal. The subject circuit monitors a voltage and generates both a current and a voltage as output signals.

US Patent:

44195427, Dec 6, 1983

Filed:

May 17, 1982

Appl. No.:

6/378517

Inventors:

Milton L. Embree - Reading PA
Dieter J. H. Knollman - Arvada CO
Earl O. Martin - Temple PA

Assignee:

Bell Telephone Laboratories, Incorporated - Murray Hill NJ

International Classification:

H04M 1908

US Classification:

179 77

Abstract:

The battery feed circuit of the present invention does not rely principally on balanced current generation circuitry but, instead, uses a feedback circuit to ensure the production of the required currents on the communication pair. The subject feedback circuit automatically and instantaneously compensates for longitudinal currents by precisely sensing the currents appearing on each lead of the communication pair. These sensed currents are summed to remove the balanced longitudinal component and the resultant signal represents the actual metallic current on the communication pair. This actual metallic current is subtracted from a predetermined reference current and the difference between these two signals constitutes an error signal which is amplified to provide the current drive supplied to the communication pair. The subject feedback circuit also includes compensation circuitry which is responsive to the common mode voltage appearing on the communication pair to adjust the amount of this generated current applied to each lead of the communication pair to thereby minimize the longitudinal potential appearing on the communication pair.

US Patent:

44737190, Sep 25, 1984

Filed:

May 17, 1982

Appl. No.:

6/378518

Inventors:

Milton L. Embree - Reading PA
Dieter J. H. Knollman - Arvada CO
Earl O. Martin - Temple PA

Assignee:

AT&T Bell Laboratories - Murray Hill NJ

International Classification:

H04M 322

US Classification:

179 18FA

Abstract:

The subject switchhook status detector is part of a battery feed circuit and functions to sense the magnitude of the current flowing on both the tip and ring conductors. The detector also generates a sum signal which represents the total metallic current flowing in the loop. The subject detector maintains the battery feed circuit in the off state until the sum signal exceeds a first predetermined threshold and, concurrently, both the tip and ring currents individually exceed another predetermined threshold. This combination of requirements prevents the generation of erroneous off-hook indications.