Abstract: In a telephone conference system, a voice switching arrangement allows a speaker who has seized the line to hear and thus permit an interrupting speaker an opportunity to talk. This arrangement is achieved in a multiparty connection by using two complementary comb filter banks on a voice channel with the filter passbands of the first bank being stopbands in the second bank and vice versa. During the time when only one speaker is talking, a full voice channel is provided for the speaker. When an interrupting speaker also begins to talk, the first filter bank is inserted in the speech signal path of the speaker who has seized the line and the second filter bank inserted in the speech signal path of the interrupting speaker such that the first speaker and the interrupting speaker receive the other's speech signals.

Abstract: A voice-actuated switching system selectively connects multiple microphones to an audio line in accordance with the output signal levels from each of the microphones. The state of each microphone is determined by its use and can exit in one of three states: selected, mixed, or off. The microphone with the greatest output signal level at any given time is considered in the selected state and is selected for connecting to the audio line with no loss. Those microphones in the mixed state have their output signal levels attenuated before being connected to the audio line. And those microphones in the off state have their outputs essentially disconnected from the audio line. The user of a microphone while in the mixed state can be heard along with the user of a microphone while in the selected state although at a lower level.

Abstract: A method and apparatus, comprising a video data bus (8), a plurality of video memory modules (VM1-VMN), and bus arbitration circuits (BAC1-BACN) associated with each video memory module, are disclosed for compiling digital image information for display. A data processor (1) addresses the plurality of video memory modules over a processor data bus (2), the data processor for assigning a priority value to picture element data stored in the video memory modules. Upon command of the data processor, a frame (5 to 300) of picture element data is serially compiled on the video data bus (8). Data contention between video memory modules for access to the video data bus is controlled by the bus arbitration circuits, the picture element data bidding with the highest priority value gaining access. In one embodiment, the priority value represents the depth of a point of a solid object for display and/or the relative depth of picture element data comprising the object for display.

Abstract: A portable frequency modulation transmitter (1) for voice or data is disclosed for operation at infrared frequencies. The transmitter comprises keyboard (200) or microphone (402) input capability and dual modes of use. In the data mode, carrier is generated when the keyboard is operated and is not generated when the keyboard is idle in order to conserve power. In the voice mode, either voice or data may be transmitted, data having priority over voice. A series connection of two variable modulus counters (302, 303) and other counters (304, 305, 306) provide a frequency shift keyed data signal, marker data signal, marker data frames between data frames, parity insertion and other features. In the event that the local battery power level falls below a particular level, a particular word is inserted in the applied binary data input.

Abstract: A method and apparatus for compactly describing an image made up of concatenated lines or filled polygons. The drawing of lines for the image begins at an initial drawing point determined in a coordinate system defined by a unit screen and proceeds from point to point with the relative coordinates of each successive point specified as a positive or negative step in the horizontal and/or the vertical direction from the previous point. The step size parameters which separately define both the amount of a change in the horizontal direction and the amount of a change in the vertical direction are initially specified in fractional parts of the unit screen and remain constant in magnitude throughout the operation. The image is reflected about the horizontal axis and about the vertical axis simply by changing the sign of the step sizes. Turning on and off the drawing process is also facilitated.

Abstract: A flickerless video display for a gray scale image is obtained using binary picture elements in an interlaced field format. The flicker is eliminated by causing each display point on a line of the interlaced field to be vertically paired with and have an intensity equal to a display point which is located on an adjacent line. Incorporating this arrangement into a display system involves a modification only to the transmitter.

Abstract: A keypad logic interface circuit (200) provides a switch closure output signal representative of a selected one of a plurality of digits on a crosspoint contact array keypad (100). The selected one of the plurality of digits provides the switch closure signal by diverting a source current (225) from a first to a second direction. The circuit encodes each one of four column outputs from the keypad into a two-bit code. An output signal from two or more columns at the same time causes the circuit to produce an inhibit output signal reflecting a multiple button-push condition. The circuit also encodes each of four row outputs from the keypad into a two-bit code and produces an inhibit output signal when multiple row output signals are received.

Abstract: In an automatic remote meter reading system, a tamper protection circuit (101) provides an alarm signal at a central station upon the disconnecting or tampering with a remote utility meter (100). Tamper protection is provided for the meter and for the transmission line carrying energy usage information to a transponder (500) such that any interruptions of the circuit path causes an alarm to be generated. The circuitry includes a remote resistance (132) associated with each meter to be protected. The value of the remote resistance is continually compared with a resistance (110) having a given value within the tamper protection circuit such that for any changes in the value of the remote resistance, an imbalance in the tamper circuit occurs and the alarm signal is generated.

Abstract: In a multifrequency generator providing tone signaling for a telephone, the common switching functions are performed by solid state switching circuitry (1200). Improved signal transfer between the telephone line and transmit and receive transducer of the telephone is provided by arranging the solid-state transmit and receive switches (1201, 1401) in a gain configuration to increase the level of the speech signal. The tone signals are digitally synthesized and use an integrated R-C oscillator (600) as a reference. Button down and button up debouncing of a contact closure signal from a single contact per button keypad is provided.

Abstract: A display illuminating circuit for a repertory dialer telephone set allows for a subscriber to operate a desired repertory button in low ambient light emergency situations. The circuit illuminates the desired buttons by distinguishable colors of light-emitting elements. Activation of the illumination circuit occurs in response to the telephone set going off-hook and then only for a limited period to conserve battery life. A battery voltage monitoring arrangement provides an indication when a local battery needs to be replaced. In response to an activation signal provided by the voltage monitoring arrangement, the light-emitting elements flash at a level that is detectable by the subscriber going off-hook even in normal ambient light conditions.

Abstract: In a remote meter reading system, a tamper protection circuit provides a warning at a central station upon the disconnecting or tampering with a remote utility meter. Tamper protection is provided for the meter and for the transmission line carrying energy usage information to a transponder (500) such that any interruption of the circuit path causes an alarm to be generated. The circuitry includes an encoder (302) associated with each remote meter (300) to be protected and a centrally located decoder (350) for receiving the signal transmitted by the encoder. When usage information is not being transmitted, the encoder is considered to be in a quiescent state providing a pulsed carrier signal to the decoder. For the transmission of usage information, the encoder modifies the pulsed carrier signal by causing a single pulse of a greater period to be superimposed on the carrier and transmitted therewith over the line to the decoder.

Abstract: In a subscriber telephone set, an active speech network provides a sidetone signal and for equalization of the transmit and receive signals at the tip and ring line port and also maintains the dc voltage at a substantially constant level at this port. The network is compatible with conventional telephone sets and operation on long loops in parallel with such sets is provided for. Internal circuitry (320) within the network check both loop current and tip-to-ring voltage to ensure that both are of a magnitude sufficient for a tone signaling dial (301) to properly generate tone signals before enabling the dial.

Abstract: A high voltage breakdown test circuit for testing of insulation resistance within an electrical device is disclosed. Operator safety is attained by allowing a fixed amount of energy considered nonlethal and advantageously imperceptible into the test circuit and by the internal system design. The system elements are connected in series and must all function properly in order to deliver the output signal to the device under test. Each system element obtains its power from the fixed energy input and is thereby activated only during an actual test. Indicator means of the pass/fail type provide an operator with a quick visual indication of the results of an insulation resistance test.