Abstract: A communication system includes a plurality of station sets each connected over two pair communication facilities to a control module. An adapter unit switchably connects an external data or voice device via a station set to either facility in response to a control signal from the control module. A data mode is established by sending a data mode request signal from the station set to the control module. An off-hook signal from a connected data device is used to request a data call. The control module signals to which facility the adapter is to connect the data call and outputs a unique visual on the data call facility. The control module prevents other calls from bridging onto or interfering with the data call. The system also permits a voice call on a facility to be converted to a data call on the other facility. Furthermore, a user can make a voice call over one facility while a data call is in progress on the other facility.

Abstract: A voltage comparator (10) includes two sampled input networks connected in arallel between an input reference voltage (Vref) and the inverting input (16) of an integrator (12,14), the other input (18) of which is grounded. The first input network has a first input capacitor (C1) which is through-switched at a first sampling frequency (F1). The second input network has a second input capacitor which is diagonally-switched at a second sampling frequency (F2), thus providing an output voltage to the integrator (12,14) which is of opposite polarity to that of the first network. For a given ratio between the capacitors (C1,C2), the output (15) of the integrator is determined by the relationship between the sampling frequencies (F1,F2), thus providing a comparator capability. Also disclosed is a frequency lock loop (34) in which the output (Vcontrol) of a frequency comparator (38) is filtered of the switching frequencies and utilized as the control voltage for a voltage controlled oscillator (42).

Abstract: A communication system includes station sets having one or more function enable buttons and a plurality of line access buttons. The function enable buttons include the extension, transfer and send message buttons. Each line select button is associated with a communication line and with the station set associated with that line. Operation of a function enable button initiates the feature associated with that button and also changes the function of a line select button from a line access button to an auto-dial select button for dialing the station associated with the line select button.

Abstract: A receiver circuit uses switched capacitor circuits to couple signals received over a communication facility to connected apparatus. During a first time interval a capacitor is connected across each lead of a facility to sample the facility voltages. During a second time interval these capacitors are disconnected from the facility lines and reconnected in series as the input to a voltage regenerator circuit. The regenerator circuit reconstructs the received signals for output to connected apparatus.

Abstract: A receiver circuit uses a switched capacitor circuit to couple either analog or digital signals received over a two lead communication facility to connected apparatus. During a first time interval, a capacitor is connected across a lead of a facility to sample the facility voltage. During a second time interval, this capacitor is disconnected from that lead and reconnected in series between the second facility lead and the input to a voltage regenerator circuit. An appropriate regenerator circuit is selected to reconstruct either the received analog or digital signals for output to connected apparatus.

Abstract: A ringing signal reformatting circuit detects ringing signals having one or more ringing bursts and generates a code representing a modified distinctive ringing signal having a predetermined number of bursts and a predetermined on/off timing in response to all detected ringing signals having the same number of ringing bursts. This coded ring signal is sent to a station set and decoded thereat to generate a distinctive ring signal.

Abstract: A trunk circuit interfaces a multichannel data signal to a communication facility using a high priority queue (HPQ) memory, a low priority queue (LPQ) memory, and a data packet sorter including a separate LPQ counter for each data channel. Each LPQ channel counter keeps track of data packets from the associated channel which are stored in the LPQ memory. The packet sorter sorts data packets according to size. Small data packets from each channel which are smaller than a predetermined length are sorted for storage in the HPQ memory only when the associated LPQ channel counter is zero. Small data packets having a non-zero LPQ channel count and large data packets are stored in the LPQ memory. The trunk circuit first transmits data packets from the HPQ memory and then from the LPQ memory.

Abstract: A self-oscillating switching regulator includes an inductor which is switched across the input or output depending, respectively, on whether a control voltage does not or does exceed a predetermined threshold. The control voltage is generated from a predetermined sum of the output voltage and a voltage dependent upon the inductor current when the inductor is connected across the input.

Abstract: There is disclosed a communication system and operating method wherein the manner in which all telephone calls are displayed at a station set allows uniform user operations to originate and terminate those calls. This is accomplished by having all calls dynamically assigned to the same set of general call appearances (buttons on a multibutton station set). There are no call appearances that are dedicated to specific call types. This allows the station set user to perform the same set of operations on all calls by using the same sequence of physical operations independent of the type of call. Additionally, the system may reserve one call appearance button at a station set for special use.

Abstract: The present administration arrangement disables any idle system apparatus which would be affected by the administration changes being made. In the station administration mode once the selected station is idle it is held in a forced idle state until administration is completed. During the system administration mode all idle stations are held in the forced idle state and all idle central office lines are placed in a forced busy state until system administration is completed. Station visual and audible signals indicate the administration status to system users. At the conclusion of administration, any forced idle stations and forced busy central office lines are returned to the normal state.

Abstract: A video display touch detection digitizer for generating the coordinate position when the video display is touched. The light signals for the X and Y coordinate array are generated from the raster scan signals of the video display during selected periods of the vertical and horizontal blanking intervals. Vertical and horizontal mirrors reflect, respectively, the resulting row and columns of light signals across the screen of the video display where other mirrors reflect the signals to, respectively, row and column signal detectors. Control circuitry detects the resulting interruption in the rows and columns of light signals when the screen of the video display is touched and generates signals representing the touch coordinates.

Abstract: An image recognition system uses feature or attribute matching for fast coarse selection of a group of reference images which closely resemble an unknown image and thereafter selects the best reference image match from that group using 2-dimensional intensity correlation or template matching. The system provides highly accurate image recognition without resorting to time consuming exhaustive search by template matching.

Abstract: In private PBX communication systems the number of dialing digits required to establish a connection between stations at different PBXs of the system includes PBX location code digits and station address digits. Abbreviated dialing is accomplished by using one or more digits of the PBX location code as both location code digits as well as part of the digits which comprise the station address.

Abstract: A data communication method and circuitry which uses a compatible subset of a standard high level data link control (HDLC) protocol to control link level communication between a digital terminal and a switch. The use of the subset of HDLC protocol reduces the complexity of the digital terminal design while maintaining communication compatibility with a switch which uses either the standard HDLC protocol or the subset of HDLC protocol.

Abstract: There is disclosed a modular memory cell structure including a data latch, an occupancy bit latch and control logic. Each memory cell has access to the occupancy bit status of adjacent cells and to the input, output, control, and status busses. The occupancy status provides positional address information enabling each cell to determine if data in its data latch is the first, intermediate, or last element of a data queue. When a group of memory cells and an initialization circuit are interconnected, a modular integrated circuit design results which can function as either a first in-first out (FIFO) or a last in-first out (LIFO) memory.