Abstract: A method of protecting computer software is provided by storing a first key in a plug-in hardware device, storing an algorithm for processing a purality of keys including the first key in software to be protected, loading the software containing the algorithm in the computer and plugging in a hardware device in a communications port of the computer. A second key, external to the software, to be protected which bears a relationship to the first key by the algorithm is loaded into the computer where processing takes place of the first and second keys in the algorithm for deriving a control key, if present, for the continued processing of the software being protected. The step of loading the second key is performed using a computer keyboard, any input/output port, a hard disk file or any other method of entry in the computer. Additional keys external to the software which bear a relationship to the first and second keys configured in the algorithm may be provided.

Abstract: A hardware device containing a first permanent key and a second key is plugged in a specified port of a computer to establish a communication path between the hardware device and computer. The first and second keys are presented with an access sequence from the computer in the software which is desired to be controlled generating outputs which are applied to an algorithm decoder which provides a control key which is used to protect the software from unauthorized use. The control key is the resultant of the algorithm decoder and the first and second keys. One of the keys is supplied with the hardware under the control of the developer whereas the second key may be supplied with the hardware device but is not restricted to the hardware device and may be entered through a separate port of the computer. The algorithm decoder can be included in any part of the software, the computer hardware or any combination thereof.

Abstract: A communication system is provided which allows closed circuit television pictures to be transmitted from conventional TV cameras to conventional monitors via an ordinary pair of wires, for example, telephone wires, lamp cord, BX cable, etc., over limited distances without measurable degradation of picture quality. A balanced system is provided with dual inputs and outputs so that the system can accommodate simultaneous transmission of audio or other data. Adapters are provided on the receiving end and on the sending end which provide conversion, impedance matching, and the frequency compensation required in order to provide uniform frequency response for the quality transmission of television as well as audio and/or other data.