Abstract: A teaching system provides explanatory materials, examples, and problems on an interactive basis and adapts to the student. The system can generate random questions for presentation to the student as multi-step examples or practice problems. The student's answers during each step of a multi-step practice problem can be evaluated to identify weaknesses. Identified weaknesses can be remedied by presenting additional explanations, providing additional practice problems, and revisiting the weaknesses by inserting practice problems of the identified type into the student's subsequent lessons. The system can also adapt adjusting the speed or number of steps presented according to the student's performance. The system can further provide detailed analysis or diagnosis of the student's performance that can be communicated to teachers and/or parents for use in other teaching environments. The teaching system when embodied in a web site further provides communication among students, teachers, and parents.

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.