Abstract: A status word modification device. A serial communications device (11) contains two universal asynchronous receiver transmitters (UARTs) (14, 15). Each UART contains a first in, first out (FIFO) buffer (14a), two status buffers (14b, 14c), and a FIFO control register (14d). If the applications program in the host (10) is an enhanced application program which supports the use of the FIFO buffer (14a), then the program will cause FIFO enablement instructions to be written into the control register (14d). In this case, the interface circuit (22) allows the status words to pass unaltered whenever the host (10) reads the status buffers (14b, 14c). However, if the applications program is a standard applications program which does not support the use of the FIFO buffer (14a), then the program will not write to the control register (14d).

Abstract: A data flow controller (150) for monitoring and automatically controlling the flow of serial data from a remote transmitter to a host device. A serial communications card (11) provides an interface between a remote transmitter connected to a serial port connector (20) and a host device (10). The card (11) contains a UART (14) which has a buffer. A counter (151) counts the number of bytes received by the UART (14) since the last time that the host (10) read all the data in the buffer. If the number exceeds a predetermined portion of the buffer capacity the counter output (Q11) will go high, thereby disabling the counter and sending a control signal (DTR, RTS) to the remote transmitter to stop sending data. Once the host (10) has read all the data in the buffer the UART (14) provides a signal (-RXREADY) which resets the counter (151), thereby causing the output (Q11) to go low, thereby allowing the remote transmitter to resume sending data.

Abstract: A method for communicating with a plurality of hosts connected to an X.25 network and for selectably using a character as a control character or a data character. Each character received from the X.25 network is inspected to determine if it is one of a set of reserved characters. If so, the character is encoded before being sent to its final destination. Data intended for the X.25 network is inspected for the presence of a predetermined control character. If the control character is present, the next character is inspected to determine whether it is a command character or an encoded data character. If this next character is an encoded data character, it is decoded and provided to the X.25 network. If this next character is a command character, then the command is executed. The method allows the use of any character as either a command character or data character. Data transfer between the DTE and DCE is assigned a PAD and a virtual channel number which corresponds to a particular host on the X.25 network.

Abstract: A direct sequence spread spectrum transmitter and receiver can be synchronized when the timing reference frequency is less than or equal to the data sampling rate and the ratio of the data sampling rate to the timing reference is an integer by combining two, four or eight consecutive data samples to yield one data sample point. By combining these data samples, an optimum data sample point may be determined while receiving an alternating sign preamble by comparing the magnitudes of all possible summations and selecting the sample which gives a maximum output. If each sample is assigned to its own synchronization point, then synchronization may be accomplished by locking to the time that gives the maximum output.

Abstract: A plurality of transmitters synchronized to a common clock each transmit a data signal spread by a common bipolar pseudo-random code having a different assigned code sequence shift. A receiver, synchronized to the clock, discriminates the signals transmitted by a predetermined transmitter from signals transmitted by the others by generating a first pseudo-random code that is a replica of the common bipolar pseudo-random code and has a code sequence shift corresponding to that of the predetermined transmitter, and a second bipolar pseudo-random code that is a replica of the common bipolar pseudo-random code and has an unassigned code sequence shift. The difference between the first and second bipolar pseudo-random code sequences, which is a trinary code sequence, is cross-correlated with the incoming signals. The cross-correlation despreads only the signal having the predetermined code sequence shift.

Abstract: A demand recorder includes a microprocessor for receiving data pulses representative of measured events and formats the incoming data into demand intervals. After a predetermined number of demand intervals, called a collection period, the microprocessor transfers the data for more permanent storage to a solid state memory which may be removed for remote processing. The system has battery carryover during a power outage, but the microprocessor prevents data transfers to the solid state memory. At the end of a collection period in which a power outage occurred, the microprocessor transfers the current data to a secondary portion of random access memory. For subsequent demand intervals until power is restored and including any thermal recovery periods, the processor formats event data by assigning index numbers for demand intervals in order of occurrence and stores data only for those demand intervals in which power consumption was actually measured.

Abstract: In a solid state current, power or energy meter having a Hall element magnetically coupled to line current, a system for compensating the Hall voltage for its dependence on temperature comprises a read only memory (ROM) containing experimentally obtained temperature compensation data. The temperature of the Hall element is measured by a thermistor to develop a temperature dependent voltage. In one embodiment, the Hall element voltage and temperature dependent voltage are digitalized and supplied to address the ROM to generate a temperature compensated Hall voltage. In a second embodiment, the ROM is addressed by only the temperature dependent voltage to generate a correction voltage that is added to the Hall element voltage for temperature compensation.