A playback device 10 generates a pseudo random noise (PN) code with a start timing based on a video sync signal, and generates a PN inverse code which has a reverse polarity to that of the PN code with a timing based on the video sync signal. An anti-duplication control signal is spectrally spread using this PN code, superimposed on the video signal and supplied to a recording device. A PN inverse code which is the same as the PN inverse code used in the playback device is also generated in the recording device based on the video sync signal, and reverse spectral spread is performed using this PN inverse code.

One or more interrogating commander stations and an unknown plurality of responding responder stations coordinate use of a common communication medium. Each commander station and each responder station is equipped to broadcast messages and to check for error in received messages. When more than one station attempts to broadcast simultaneously, an erroneous message is received and communication is interrupted. To establish uninterrupted communication, a commander station broadcasts a command causing each responder station of a potentially large first number of responder stations to each select a random number from a known range and retain it as its arbitration number. After receipt of such a command, each addressed responder station transmits a response message containing its arbitration number. Zero, one, or several responses may occur simultaneously. By broadcasting requests for identification to various subsets of the full range of arbitration numbers and checking for an immediate error-free response, a commander station can determine the arbitration number of every responder station capable of communicating at the time. Consequently, a commander station can conduct subsequent uninterrupted communication with each responder station, for example by addressing only one responder station. Responder stations of this invention require minimal logic and circuitry to respond to multiple commander stations.

A system for wireless communication between a plurality of semiconductor chips is disclosed. Each data line in the present invention is coupled with a transmitter for transmitting information to any other semiconductor chip. Furthermore, each data line is coupled with a receiver for receiving information transmitted by any transmitter. The system also comprises multiple antennas, fabricated from the chip's metalization layer. Nonetheless, separate antennas within the chip packaging can also be used. The antenna unit comprises a dipole and a loop antenna in a planar arrangement, thereby forming a spherical electromagnetic pattern of coverage and making the orientation between semiconductor chips for transmission purposes substantially irrelevant. Each transmitter in the system comprises a modulator for modulating the information being transmitted, while each receiver comprises a demodulator for demodulating the information transmitted. Several modulation schemes can be employed, though amplitude modulation is preferred, whereby each transmitter has a distinct carrier frequency within the operative radio frequency spectra--preferably above 900 MHz. Each transmitter and receiver is coupled to a power source comprising a capacitor, as a signal generator, and a rectifying circuit. To ensure that the communication between chips is noise/interference free, the entire system is shielded with a metal housing.

A protocol for wireless direct user-to-user DSSS TDMA digital communication at a data rate of the order of one to several megabits per second in the 902-928 MHz, 2400-2483.5 MHz or 5725-5850 MHz band includes a sequence of transactions, each transaction consisting of a predetermined sequence of subpackets, and each subpacket consisting of a predetermined number of bytes preallocated to a subpacket element or element portion. Network communications among a plurality of stationary and/or mobile users such as personal computers, each equipped with a (Remote Unit) transceiver, are organized and directed by a Master Unit transceiver. Master Unit and Remote Unit transceivers have identical circuitry. Using a first pseudorandom code sequence (M-code), the Master Unit intermittently transmits a DSSS signal enabling Remote Units to synchronize to the Master Unit and so receive scheduling directives. A Remote Unit, while maintaining synchronization with the Master Unit, sends information by transmitting a DSSS signal using a second pseudorandom code sequence (R-code). To facilitate synchronization, the Master Unit also transmits a continuously running DSSS signal using a third pseudorandom code sequence (P-code) which is code-locked and phase-locked to the M-code. A transceiver implementing the protocol in the 2400-2483.5 MHz band includes a microprocessor, external data RAM, Control Logic Section, Analog Section, and Radiofrequency Section.