Abstract: A speech control circuit is disclosed for use in a loudspeaker telephone or a handsfree telephone having a microphone and a speaker, and provides the correct switching of the transmission mode and the reception mode in spite of acoustic coupling between the speaker and the microphone. The disclosed circuit reduces errors in the switching operation and helps to prevent the problem of "noise block".

Abstract: An improved equalizing system for modifying an input electrical signal representative of original sound so as to correct for the inherent nonflat frequency response of an audio signal processing apparatus and the acoustic effects of listening environment in which the loudspeaker system of the audio signal processing apparatus may be disposed. The improved equalizing system includes a comparator for comparing the signal energy in each of a plurality of select frequency bands of a predetermined frequency range of the input signal with that of the corresponding signal energy in a like plurality of bands of a like range of a second signal representative of the acoustic output of the loudspeaker system and as a function of the nonflat frequency response and the acoustic effects of the environment. A correction signal representative of the comparison is used to modify the energy within each band of the input signal so as to substantially correct for the nonflat response and the acoustic effects of the environment.

Abstract: This electronic ring sounder utilizes the loudspeaker and audio amplifier present in a speaker telephone to accomplish the bell sounding function. To this end, the amplifier is provided with a feedback circuit which, when enabled, causes the amplifier to oscillate in the audio frequency range. The feedback path includes a gate which is enabled in response to presence of the ring tone on the telephone line. Advantageously, the oscillation frequency is on the order of 1,000 Hz, and is gated on each half cycle of the ring signal. This produces a sound which closely simulates that of a conventional telephone bell.

Abstract: This telephone answering device has facilities for the remote controlled playout of previously recorded incoming messages. In response to receipt of a coded signal, a cam control mechanism positions the message tape drive motor first to rewind the incoming message tape, and then to drive the tape forward for remote playout of the messages. The control mechanism is configured to sense whether the tape drive motor is correctly positioned at the beginning of an answering cycle. If not, the cam control mechanism is actuated quickly to correctly position the tape drive motor. Thus the answering device will operate properly even in the event that the cam control mechanism was left in an improper position during the previous answering or remote playout cycle, for example, as a result of a power interrupt during that cycle.

Abstract: The disclosure shows a telephone range extender which is automatically adaptable to the length of the connected subscriber loop. A loop resistance detector within the range extender discriminates between loops within a plurality of ranges of lengths. For extremely short loops not requiring range extension, the range extender circuits are disconnected from the loop. For intermediate length loops, the gain of a bidirectional voice frequency amplifier is set at a low value to provide just sufficient gain for these loops. For longer loops, the gain of the amplifier is increased to provide sufficient amplification for the longer range. For extremely long loops, the range extender is disconnected since such loops must be served by remote amplification facilities. An automatic range extender of this type is shown connected behind the first stage of the central office switch in order to concentrate range extenders on a larger plurality of subscriber loops.

Abstract: A dual-tone multiple frequency signal generator is provided for use with telecommunications systems, data transfer systems and other applications. The tone encoding system utilizes MOS/LSI integrated circuitry on a single chip powered directly by telephone line voltages. An electronic keyboard circuit provides synchronized pulses to decode single-pole, single-throw keyboard switches by row and column. A crystal-controlled oscillator generates a reference frequency which is divided according to the row and column of an activated keyboard switch to obtain two pulse signals having frequencies representative of the activated switch. The outputs of the divider circuitry are fed to a programmed logic array which generates two digitally coded signals each representing a sinusoidal waveform. A digital-to-analog ladder network converts the digitally coded signals to continuous sine waves, and an operational amplifier combines the sinusoidal waveforms to provide a dual-tone output.

Abstract: Circuit apparatus for supplying a regulated loop current to a two conductor loop telephone line includes first and second line feed resistances, each having one terminal connected to a respective terminal of the telephone line. A differential amplifier has one input connected to the first resistance and a second input connected to the second resistance in common with the resistance connections to the telephone line terminals. One of the resistances has its other terminal connected to the output of an active circuit means, which circuit operates in a feedback path to supply the desired loop current to the line resistance and therefore the telephone line. The input control signal for the active feedback circuit is derived from summing the output signal from the differential amplifier with a reference signal whose magnitude varies according to the length of the telephone line.

Abstract: A solid state subscriber station network which provides transmitting, receiving and regulating functions using a single active element. The transmitted signals, the received signals and the regulatory functions can be separately varied within proscribed limits without adversely affecting the other functions.

Abstract: Apparatus for remotely supervising via a telephone line a device includes a sensor for sensing for a telephone ring signal from the telephone line. In response to the sensing of the ring signal there is generated an off-hook condition which causes the termination of the ring signal. In addition an indicator responsive to the sensor produce a melody continuously repeated with an interval between each transmitted melody. This repeated melody is transmitted to the telephone line for counting by the caller. In addition, within the apparatus, a counter counts the melodies as they are produced. A key memory connected to the counter and responsive to the telephone line is activated when a predetermined count has been counted by the counter and there is a voice signal on the line from the caller. The operation of this key memory alerts a control circuit for the reception of subsequent voice signals which permit the changing of state of a controlled device.

Abstract: An electrically programmable memory array having rows and columns of floating gate type memory cells employs alternate output lines and ground lines between the columns of cells, providing a virtual ground arrangement. A row is selected by one part of an address input, and a column selected by another part. An output line on one side of the selected column is activated, and a ground line on the other side. A differential sense amplifier is responsive to the voltage on the selected output line and a reference voltage. A power down mode of operation is provided in which current flow in various circuits of the device is greatly reduced. To speed up access time in exiting from power down, the reference voltage input to the sense amplifier is shifted during power down then when exiting returns to its operating value according to a time constant.

Abstract: An automatic telephone answering system wherein disconnection from the telephone line following calling party hang up is in response to the detection of dial tone, utilizes a signal detector responsive to voice and steady tone signals for providing an indication of the status of an incoming signal on the telephone line, and a processor for monitoring line signal status to determine the presence of dial tone. Following a determination of the presence of dial tone as an incoming line signal, the processor acts to automatically disconnect the system from the telephone line by opening a telephone line connection relay. The determination of dial tone is made based upon the continuous existence, over a predetermined time interval, of an incoming line signal status representative of a steady tone signal, rather than an absolute, single event detection.

Abstract: A bias control circuit adapted to be utilized with complementary, tracking current sources for use in an audio reproduction system including volume and tone control circuits to optimize the signal to noise ratio of the system at maximum gain without compromising the signal handling capabilities of the system. The bias control circuit includes an interface circuit responsive to an applied volume control signal for varying a bias signal connected to the output of the interface circuit. A second and third circuit are coupled with the output of the interface circuit which are responsive to the bias signal for deriving, respectively, a volume output signal to control the gain of the volume control circuit and a current biasing signal for controlling the bias levels of the tone control circuits. The current biasing signal varys proportionally with increases in the volume control signal from a first level to a second level remaining constant thereafter.

Abstract: A transmission arrangement for use in a customer premises communication system is operable for controlling transmission during the MF digit signaling interval in situations where it is necessary to convert station dialed MF signals to pulsed digit signaling. In systems where the signaling station, the MF to dial pulse converter and the Central Office or PBX line are bridged on the same communication link it is possible for the station's MF signals to be detected by the MF receiver in the Central Office, thereby causing errors in the received digits. These problems are eliminated by inserting two transmission gates in the four-wire portion of the CO line. The gates are controlled by the processor in the customer premises communication system such that the outward gate is opened immediately upon seizure of the line by the calling station and remains open during the entire dialing interval.

Abstract: A throat microphone consists of a dynamic pressure transducer sealed within an airtight tympanic enclosure to be held by an elastic band on the user's throat near the voice box. The electrical signals generated by the transducer are applied as an input signal to an amplifier and speaker unit where the signal is conditioned by a preamplifier stage for further amplification by a second stage that contains a variable reactive negative feedback network that acts as a low pass filter and corrects the phase shift of the different lower frequency audio signal components while emphasizing the higher frequency components so that severe phase distortion of the signal applied to the drive speaker through an output power amplifier stage can be minimized to make the speech sounds reproduced more intelligible.

Abstract: A video tape recording apparatus with the use of an Hadamard transformation system is disclosed. The apparatus comprises means for distributing the video signal to a plurality of channels, means for recording and reproducing the distributed video signals by plurality of magnetic heads, means for synchronizing a time-base correction signal for time-base correction with a sampling signal for Hadamard transformation, and means for phase-controlling a sampling signal for Hadamard inverse transformation to the time-base correction signal in phase.

Abstract: A directional array of acoustic transducers is disclosed. The acoustic transducers are arranged colinearly and in pairs symmetrically about a center line of the directional array. The distances of the acoustic transducers on either side of the center line of the array are neither linear nor monotonic. These distances are calculated using a recursive far field response formula which effectively reduces sidelobe magnitudes to a desired design amplitude envelope. The response produced is highly directional, comprising one main lobe and a plurality of sidelobes each less than the desired design envelope, which is substantially lower than the main lobe but of arbitrary (e.g., stepped) shape.

Abstract: In a video disc player intermodulation distortion can occur during signal recovery and is manifested as the modulated sound carrier appearing in the baseband video. To reduce such distortion, a portion of the signal recovered from the disc record is filtered to extract the modulated sound carrier. This signal is applied to a phase shifting circuit having a predetermined frequency response to condition the modulated sound carrier to have a phase characteristic substantially similar to the phase response of the modulated sound carrier appearing as distortion in the baseband video. The phase conditioned sound carrier is then amplitude adjusted and linearly subtracted from the baseband video signal.

Abstract: An electronic tone ringer for use in telephone substations. This circuit operates in response to conventional ringing signals and generates a single tone alert signal interrupted at a low frequency. The audible tone alert signal is generated by a piezo-ceramic transducer.

Abstract: An improved loudspeaking substation circuit employing a dual-tone multi-frequency signal generator wherein output tone levels are regulated by the substation transmission circuit when operating in either a loudspeaker or handset mode. The circuit further provides for preventing acoustic feedback and self-oscillation between the loudspeaker and handset transmitter while transferring between either mode.

Abstract: A magnetic tape reproducing and/or recording system in which two magnetic cassette tape transports are mounted on the same chassis and are adapted to selectively drive magnetic tape from two separate type cassettes past separate head assemblies to reproduce and/or record magnetic signals on the tape. The arrangement is such that the second tape cassette is automatically actuated upon the tape in the first cassette reaching its end, and vice versa. Logic circuitry is provided which controls the tape transports so that, after completion of the first cassette tape it can be rewound to a starting position during play of the second tape, and vice versa. A single set of recording and playback electronics can be provided which are automatically switchable between the respective head assemblies depending on the particular operational mode.