Abstract: In a data processing system that includes a central processing unit (CPU) which performs functions on data characters based upon a set of program instructions, the central processing unit being of a type that includes: (a) an arithmetic logic unit for performing the functions on the data characters; (b) a plurality of internal registers for storing data characters; (c) a data bus both for transferring data characters internally within the CPU and for transmitting data characters to and receiving data characters from devices external to the CPU; and (d) an address bus for transmitting receiving addresses of referenced program instructions, and wherein the contents of one of the internal registers forms part of the address of the referenced program instruction available on the address bus.

Abstract: A radio frequency modulator/demodulator (modem) and method for receiving and transmitting data over a radio frequency data link. The modem has a transmitting section which includes a modulator which modulates a radio frequency signal in response to data provided by, for example, an associated processor. The transmitting section further includes a watchdog or enable circuit which monitors a request-to-send signal produced by the associated processor, with the request-to-send signal being present when the processor is generating data to be transmitted over the data link. The enable circuit will disable the modulator should a transmission exceed a maximum predetermined time period, thereby preventing the associated processor from monopolizing the data link in the event of a processor failure.

Abstract: An improved telephone bridge apparatus of the type in which a plurality of remote stations communicate with a local station over a plurality of phone lines, wherein each of the plurality of phone lines is assigned to a different one of the plurality of remote stations. Each phone line is connected to an input channel, and each input channel is summed at a summing point, and the collective signal is supplied to a modem. Each phone line is connected to an output channel, each output channel receiving the same broadcast message from the modem. The modem, in turn, is connected to a controller, which communicates with the local station and which polls the remote stations according to a predetermined priority. The improvement includes monitoring means for measuring the signal levels being transmitted along each input channel, and signal level modifying means positioned in the signal paths of each input channel for modifying the level of the signal being transmitted thereto.