PHILIP L MARTIN, M.D.
Medical Practice at Blue Ridge Rd, Raleigh, NC

4577255, Mar 18, 1986

Jun 20, 1984

6/622432

Philip T. Martin - Raleigh NC

ITT Corporation - New York NY

H02H 904

361119

A lightning protection circuit for a digital subscriber loop interface has a loop interface transformer primary, connected across the TIP and RING terminals of the DSL interface, with a split winding. The split primary windings are balanced to minimize induced secondary voltages in the event of common mode lightning signals. Matched TIP and RING resistors limit the lightning current flowing to lightning ground. Back-to-back zener diode pairs across each split winding, and a capacitor connecting the split windings, limit the voltage across the windings in the event of differential lightning signals. The capacitor absorbs most of the lightning energy, rather than the secondary windings or the resistors. Back-to-back zener diode pairs across each secondary winding provide further lightning protection by limiting the energy absorbed by the transmit and receive circuitry. A resistor and diode configuration is used to protect the DSL interface analog switch and power supplies of the receive circuitry, and a diode may be used to protect the -5 volt power supply of the transmit circuitry.

4622442, Nov 11, 1986

Jul 13, 1984

6/630801

Philip T. Martin - Raleigh NC

ITT Corporation - New York NY

H04B 158

379402

An electronic hybrid circuit for coupling a two-wire communication path to a four-wire communication path includes amplifier circuits having a reactive feedback path such that the output impedance of each amplifier is approximately zero ohms at DC and is a predetermined value at audio frequencies. The amplifiers are arranged to provide battery and voice signal injection on the two-wire path. Serially connected diodes provide protection from lightning.

4622441, Nov 11, 1986

Jun 21, 1984

6/623267

Philip T. Martin - Raleigh NC

ITT Corporation - New York NY

H04B 158

379345

A subscriber line interface circuit is provided for a telephone system for interconnecting a two-wire telephone channel with a four-wire telephone channel. The circuit includes a pair of power amplifiers employing complementary circuitry and being coupled in complementary fashion to the two-wire channel so as to provide for both DC electrical excitation to the two-wire channel, as well as providing for an impedance match over the voice frequency spectrum, thereby reducing power dissipation while improving the coupling of voice and/or data signals. The presence of any noise on power line is rejected by use of transistor biasing circuits and by use of feedback circuitry. Both resistive and capacitive feedback branches are provided for the impedance matching.

4607142, Aug 19, 1986

Jul 27, 1984

6/635035

Philip T. Martin - Raleigh NC

ITT Corporation - New York NY

H01F 2738

179 16AA

In a transformer-coupled interface circuit for interconnecting two-wire and four-wire telephone communication channels, there are provided a bucking winding in the transformer and a flux compensation circuit which drives the bucking winding. The flux compensation circuit includes a sensor of direct current current flowing through a primary winding of the transformer for applying power to a subscriber telephone. Also included within the compensation circuit is a current source responsive to the measured primary current for controlling the magnitude of the bucking winding current to track the primary current, thereby to reduce the flux in the transformer core and permit use of a smaller sized core. A stabilization circuit within the current source prevents oscillation resulting from feedback and reactive circuit components.

4593156, Jun 3, 1986

May 18, 1984

6/611569

Philip T. Martin - Raleigh NC

ITT Corporation - New York NY

H04M 308

179 16AA

A grounded tip detector for use in a subscriber line circuit detects and indicates a tip-to-ground condition in the SLIC. Hysteresis and RC filtering are provided to assure a sharp switch-over of the tip-to-ground detection output and a reduction in the effect of ripple signals due to longitudinal currents.