Abstract: Disclosed is a security device coupled to a computing device, which is, in turn, coupled to a server through a computer network. The security device stores a serial number associated with the security device and a user key associated with the serial number. When the computing device attempts to log onto the server over the computer network, the server requests a serial number from the security device. If the serial number is stored within a user information database, the server obtains an associated user key and computes a challenge. Further, the server computes an expected response for the security device based on the associated user key. The server then sends the challenge to the security device over the computer network. If the server receives a response back from the security device that matches the expected response, the server will allow the computing device to log onto the server.

Abstract: An electric guitar amplifier which utilizes a digital signal processor to produce vacuum-tube-like distortion without certain unwanted audio artifacts created by previous digital realizations of nonlinear, high-gain functions. By virtue of a microprocessor-controlled digital signal processor embodiment, the invention gives the user programmable control over parameters normally associated with state of the art guitar amplifiers (e.g. tone controls, reverb controls, tremolo controls, etc.), as well as other musically useful parameters which are not normally included among the controls of a guitar amplifier (e.g. selection of preamp type, autovolume, reverberation type, autowah, etc.).

Abstract: A method for synchronously operating two or more rotary head digital audio tape recorders without having to dedicate a separate timing track. The present invention synchronizes the machines in three steps. First, the slave unit reads the time code value from the data stream and compares this time code to the master's time code, examining the difference in time code values and adjusting the transport speed so that the values are approximately equal. Next, the slave's capstan motors are slowed down (or sped up) so that the slave and master units are within one drum revolution of each other. Finally, the slave's microprocessor adjusts the speed of the entire system to skip individual samples until the master and slave units are synchronized.

Abstract: A method and apparatus for recording multiple channels of digital audio data onto one-half inch tape using a rotary head recorder. The tape format includes sector spaces and a write timing sector to provide reduced susceptibility to errors arising from head misalignment, provides improved punch-in and punch-out capabilities using overdub identification values recorded within each channel of audio information, and provides a unique time code word that facilitates accurate high-speed scan and search operations, as well as multiple device synchronization. Each pair of audio tracks terminates with a write timing sector that serves as an absolute location marker for the rotary head, and allows the digital audio system to determine precise head location with respect to the tape.

Abstract: A digital audio interface protocol carries multiple channels of digital audio information serially between a transmitting digital audio tape recorder and a plurality of receiving recording units. Using a three stage process, the circuitry of the present invention allows the receiving VCO's to "lock on" to the sampling rate of the serial digital data stream without any explicit sampling information. In a first stage, the VCO frequency is adjusted until a sync pattern is properly received. In a second stage, the VCO frequency is adjusted to oscillate a preselected number of times between sync pattern occurrences. In a third stage, the VCO phase is adjusted to match the phase of the serial data stream.