Abstract: An improved solid state isolation device that uses opto-isolators to provide an electrical barrier between a telephone network and user telephone equipment includes a load and current control circuit, and an adjustable termination circuit to eliminate or reduce signal distortion and insensitivity to low signal levels resulting from low loop current, and lack of complex impedance compensation/termination for diverse telephone system parameters. An improved trans-hybrid return loss circuit reduces internal losses; while loop termination losses are reduced by the use of Shottky diodes in the line coupler circuit. A high pass filter improves common mode rejection ratios in the transmit and receive paths, and adjustable compensation is provided to account for manufacturing variances in the opto-isolators. An additional connection is also provided to adapt the opto-isolator circuit for use with 3-wire ring circuitry.

Abstract: An isolation circuit (20) that is devoid of coupling transformers and yet suitable for use as a telephone line interface. The circuit is characterized by very wide bandwidth, low noise, and high linearity. Opto-isolators couple analog transmit and receive channels in a user device (12) across an isolation barrier (57) to a line pair for full duplex communication on the line pair. The interface circuit, which also includes a hybrid (55), includes first and second oppositely directed linear optocouplers (50,52). The first is disposed between the transmit channel and the hybrid; the second between the receive channel and the hybrid.

Abstract: A single unitary terminal configuration includes a card reader for reading data contained on a credit or debit card, a communications system for accessing a central database for authorization purposes, an input/output system for inputting alphanumeric data into the terminal, and for displaying audio and visual signals concerning the use of the terminal and the card's status, and a printer for printing data onto a receipt. The terminal preferably includes a fixed head magnetic card reader for reading magnetic stripes of credit or debit cards. The card reader is preferably of an insertion type having a card receiving channel opening at an edge of the terminal housing.

Abstract: An improved solid state isolation device that uses opto-isolators to provide an electrical barrier between a telephone network and user telephone equipment includes a load and current control circuit, and an adjustable termination circuit to eliminate or reduce signal distortion and insensitivity to low signal levels resulting from low loop current, and lack of complex impedance compensation/termination for diverse telephone system parameters. An improved trans-hybrid return loss circuit reduces internal losses; while loop termination losses are reduced by the use of Shottky diodes in the line coupler circuit. A high pass filter improves common mode rejection ratios in the transmit and receive paths, and adjustable compensation is provided to account for manufacturing variances in the opto-isolators. An additional connection is also provided to adapt the opto-isolator circuit for use with 3-wire ring circuitry.