Abstract: A transparent secondary information transmission system for a primary information transmission system is disclosed. The system includes at least one local condition monitor for monitoring at least one of a plurality of input conditions such as temperature, light, smoke or the presence of an intruder. The information representing the condition is digitized and processed by the local condition monitor. The digitized signals are then transmitted over the transmission system in such a way that no interference with normal transmission occurs. At the receiving end, the signals are processed to determine from which of the local condition monitors the signals are being received and what the status of the monitored condition is. A determination is then made whether an alarm should be generated. In the preferred embodiment, the primary information transmission system to which the secondary information transmission system is adapted to be coupled is a telephone network.

Abstract: An audio mixer for combining stereo phonograph, stereo high impedance and low impedance input signals having a means for audio previewing one or more of said inputs simultaneously including a means for visually indicating which signals are being previewed, further including a means for audio previewing said signals in a monophonic signal, further including a means for combining said inputs in the final amplifier stage such that the output signal is in a monophonic state, further including a means for disabling said low impedance input from the final output means.

Abstract: FM-receiver including a frequency-locked loop (2-14), which loop includes, successively connected, a voltage controlled oscillator (8), a mixer circuit (2) connected to an aerial input, an IF-portion comprising an IF-filter (9), an FM-detector (4), a loop filter (5) and a loop amplifier (6) for adjusting the transfer characteristic of the frequency locked loop (2-14), which loop amplifier (6) is connected to a control input of the voltage-controlled oscillator (8) for a feedback of the modulation signal of the received FM-signal. The loop filter (5) comprises a first low-pass filter (14). The FM-receiver being realizable in integrated circuit form and suitable for processing FM-stereo signals. The receiver is at least comparable to conventional FM-stereo receivers as regards selectivity, harmonic distortion and stability, the conventional FM-stereo receivers not being realizable in integrated circuit form.

Abstract: A stereo speaker system is shown having at least three individual speakers arranged along a path, with one of the speakers positioned between the other two speakers and connected to receive signals from a selected one of a pair of left and right signal outputs from a stereo signal source such as a stereo radio. Both of the other two speakers are connected to receive signals from the remaining one of said pair of outputs. Balanced stereo images are thus obtained simultaneously at two different locations. The system has particular application in an automobile. Another embodiment is shown which uses more than three speakers.

Abstract: An AM stereo modulator is disclosed which includes a limiter responsive to first and second audio signals for providing first and second equally limited amplitude limited signals. A quadrature amplitude modulator responds to the first and second amplitude limited signals and provides an amplitude modulated carrier signal having in-phase and quadrature-phase components modulated in accordance with the first and second amplitude limited signals, respectively. A distortion detector monitors the envelope of the quadrature amplitude modulated signal for detecting the extent to which the envelope differs from one of the two amplitude limited signals and for controlling the limiter in accordance with the extent of the difference. The distortion detector can also be used to control quadrature channel signal gain instead of the limiter. A program analyzer determines whether to control quadrature channel signal gain or the limiter with the distortion detector.

Abstract: Public alert and advisory systems for the communication of emergency and/or other information from one or more central locations to a plurality of remote locations, such as, by way of example, information regarding a nuclear accident and evacuation procedures. This system utilizes conventional programming stations such as AM, FM or TV stations, central transmitting equipment, with the emergency information being modulated by a second modulation technique differing from the first modulation technique for the ordinary programming so that conventional manually operated programming receivers will not be responsive to the emergency information. The receivers of the system however, are responsive to the transmitted emergency information, so as to sound a warning alarm, display codes relating to evacuation or other information and/or receive and present audio information depending upon the specific configuration of the system.

Abstract: An automobile equipped with the vehicular portion of a traffic information and guidance system utilizing exchange of data between vehicles and the rest of the system through inductive coupling with loops set at various places in roadways, is provided with two-way telephone communication possibilities at places where roadway loops are provided where a car can stop for making a telephone call, as for example in a parking space. Only small amounts of equipment need to be added to the vehicle and to the fixed installations to permit telephone communication between the vehicle and telephones in a public network. Separate receivers and transmitters for speech communication operated with amplitude or frequency modulation can be switched in, or else the speech signals can be converted into pulse code modulation and simply supplied through input/output units to the data transmitter/receiver of the traffic information system.

Abstract: An automatic telephone answering and recording apparatus comprising: a speaking circuit; first means operating in response to a call signal from a caller transmitted over a telephone line to connect the speaking circuit to the telephone line associated with the caller; a recording/reproducing means coupled to the speaking circuit for recording an incoming message from the caller in its recording mode of operation, and transmitting a previously recorded incoming message to the telephone line through the speaking circuit in its reproducing mode of operation; selection means for selecting the operation mode of the recording/reproducing means; and control means connected between the speaking circuit and the selection means for controlling the selection means, the control means including a voice recognition means and a previously registered specific message from a subscriber and being operative to control the selection means to select the recording mode when the voice recognition means receives an incoming message

Abstract: In a power line carrier telephone extension system for transmitting electrical signals between the telephone line and one or more extension telephones over the AC electric power line available at a telephone subscriber's premises, that includes a main station for processing signals between the subscriber's telephone line and power lines and one or more extension telephones of the system that plugs into the power line, all of which can place calls to the telephone line, answer calls from the telephone line and conference together in full duplex communication, means at the extension telephones for initiating a telephone line hold signal that is transmitted over the power line to the main station where the hold signal is detected and initiates connecting a hold impedance across the telephone line.

Abstract: A method for generating a compatible AM quadrature stereo wave by delivering a modulated carrier with in-phase sidebands generated by a first combination of two signals, and quadrature sidebands generated by a second combination of the signals, the in-phase and quadrature sidebands having substantially the same maximum amplitude. The carrier and both sets of sidebands are delivered to an envelope detector, which delivers only the first combination of signals, undistorted by the presence of the quadrature sidebands. The carrier and both sets of sidebands are also delivered to a synchronous detector, which delivers only the first combination of signals with predistortion. The output of the synchronous detector is subtracted from the output of the envelope detector to obtain as a result the predistortion of the first signal combination due to the presence of the quadrature sidebands.

Abstract: A message transmitting system incorporated in a telephone system includes a device for generating service signals relating to the making of a telephone connection between one telephone set and another telephone set and a mixer with two inputs which are connected to the service signal generating device and to a message generating device, respectively. The output of the mixer being connected to the telephone line.

Abstract: A cordless telephone including a base unit and a remote unit that are in wireless communication. The remote unit has a number keyboard whereby code numbers can be entered into the system. A pulse detecting network picks up and identifies the code numbers placed in the remote unit and, in response thereto, controls a variety of electrically responsive devices. The remote control function is carried out without interrupting the voice communication feature of the phone or tying up the subscriber's lines thus providing the user with a degree of mobility not found in similar telephone related control devices.

Abstract: A stereo sound system for reproducing signals from two independent channels through right and left speakers. The two speakers are centrally located and propagate a lesser part of their acoustic output directly into free space. Two acoustic tunnels separately couple the major part of the outputs of the respective speakers and have their issuing ends far removed on either side of the speakers. The tunnels provide advantageous delay.

Abstract: First and second rectangular signals which are 90.degree. out of phase with each other are derived by comparators and an RS flip-flop from a symmetrical triangular wave signal. The first rectangular signal is halved in frequency by a frequency divider, the output of which is supplied to an adder. The second rectangular wave signal is also delivered to the adder. An output from the adder is converted by a bandpass filter into a sine-wave subcarrier signal in synchronism with a stereo pilot signal in an FM stereo tuner. The first and second rectangular signals may be derived by a pair of D-type flip-flops from a pulse signal.

Abstract: A text mailing system comprises a plurality of terminal equipments each connected to a telephone set to input and output a message and a mail control unit for receiving the messages from the terminal equipments through an exchanger and transmitting the received messages to the terminal equipments specified by the messages. Each of the terminal equipments inputs addressee identification information and the mail control unit transmits the messages to the terminal equipments on the condition of inputs of the addressee identification information for a specified type of message.

Abstract: Filter holders and system are referred to as Fili-holders or Fili-holder system on the title page and all hereafter, so as not to be confused with any existing filter holding methods.A desired square filter is inserted into a Fili-holder and is placed on a copy camera lens collar as a unit. This eliminates the need and current use of a permanently mounted filter holder to the copy camera lens and the problems inherent from same.

Abstract: A receiving arrangement is provided, to receive audio frequency signals that are transmitted by way of lines of an alternating current distribution network. The audio frequency signals are decoupled from a low or medium voltage level of the network. The currents in one or more phases in such level are detected and the signal is applied to a receiver. The audio frequency signals are decoupled by means of one or more current transformers or voltage transformers and currents or voltages in secondary windings of signal transformers connected thereto are detected. Each secondary winding of the signal transformers with the ohmic resistance thereof and the load resistance thereof, forms a high-pass filter with the lowest frequency to be transmitted as its lowermost frequency. The signal transformer cooperates with an amplifier, summing or subtracting circuit in the receiving circuit.

Abstract: An AM stereo demodulator having monophonic and stereophonic modes of operation and adapted to demodulate a QAM signal whose quadrature-phase signal has a low frequency slot containing substantially no information signal therein. The demodulator includes a low-pass filter for filtering the quadrature-phase signal so as to provide a filtered signal containing only signals in the low frequency slot of the quadrature-phase signal. A window comparator compares the amplitude of the filtered signal with two threshold levels and provides a first output signal when the filtered signal is outside of the range bounded by the threshold levels. A circuit is included for placing the AM stereo demodulator in the monophonic mode of operation in response to the first output signal.

Abstract: The disclosure relates to an audio signal reproduction system having one or more of the following features: (1) a loudspeaker having (a) a flat frequency response and (b) a predetermined power response; (2) two loudspeakers adapted to be positioned relative to one another so that they reproduce a stereophonic image substantially independent of the listener's position along a listening line spaced from the loudspeakers and nonintersecting a line extending between the two speakers; (3) an improved cross-over network having a substantially constant input impedance as a function of frequency; (4) a power sensor for sensing the power applied to a transducer so that audio signals are transmitted over a first signal path through the system when the sensed power is above a predetermined minimum level, and over a second path when the sensed power falls below the minimum level; (5) a power monitoring circuit to prevent a loudspeaker driver from being overdriven; and (6) a circuit for substantially balancing the signal

Abstract: Disclosed is an FM stereo demodulator in which components of the demodulated signal corresponding to odd harmonics of the subcarrier signal are eliminated.In order to prevent the production of odd harmonics, the multiplication between positive and negative sinusoidal subcarrier signals is performed with a stereo pilot signal and positive and negative pulse train signals produced by pulse detection of an FM signal.The multiplication signals are further added with each other to directly reproduce left and right stereophonic signals.