Abstract: A microphone-speaker is removably attached to an article of clothing by a device having a sheet of flat material provided with a plurality of openings spaced along a circular circumference of selected radius and center. When fastened to the microphone-speaker, the openings form depressions. A flat resilient spring is pivotally attached to the sheet of material at the center and extends at least as far as the depressions so that a projection on the spring can engage the depressions. A clip is pivotally mounted on the spring in the vicinity of the projection and extends along the spring toward the center to one end of the clip. Means are provided to urge the one end of the clip toward the plane of the flat material so that the one end can be pivoted away from the flat material to permit an article of clothing to be resiliently held between the one end and the microphone-speaker.

Abstract: Dual resonator crystal filters have an input electrode, a common electrode, and an output electrode which provide two resonators coupled together. Mathematical formulas were derived to determine the resonator frequencies, the synchronous peak separation frequency, and the normalized center frequency. These formulas use selected frequencies or parameters which can be easily measured by applying a variable band of frequencies to the input electrode of a dual crystal filter. Measurements are made of the frequencies at which the voltage at the common electrode is a maximum when the output electrode is connected to the common electrode by capacity and when the output electrode is connected to the common electrode by a short circuit. The measured frequencies can be used in the mathematical formulas to determine the resonator frequencies, the synchronous peak separation frequency, and the normalized center frequency.

Abstract: A battery is held in and connected to a radio receiver by an arrangement having a hollow cylinder that fits in the receiver, and that holds the battery. The cylinder is held in the receiver by first metallic clips. An associated first spring forms the negative connector to the receiver circuit. A closure cover having a metallic portion fits on one end of the cylinder. When a battery is positioned in the cylinder, the cover connects the negative terminal of the battery through the cylinder to the first metallic clips. A metallic contact is held by second metallic clips in the vicinity of the other end of the cylinder. When a battery is positioned in the cylinder, its positive terminal engages the metallic contact and is connected to the receiver circuit through an associated second spring.

Abstract: Signals are transmitted over a line from a control location to a remote location in order to control an apparatus at the remote location. Frequently, the line is subjected to faults, such as voltages, noise, or opens. Or there may be a power failure at the remote location. Such faults or failures will probably be unknown to the user at the control location. An arrangement is provided at the control location for automatically and periodically transmitting the last selected control signal to insure that the apparatus at the remote location is operated as desired by the user.

Abstract: Conventional paging receivers are provided with a circuit which, when a predetermined paging signal is received, produces an audible sound that alerts the user that he is being paged. The audible sound continues until the page is completed or until the user presses a reset button. In some situations, the audible sound is undesirable or unacceptable. This invention includes a switch which, in a store position, prevents the receiver from producing an audible sound when a paging signal is received. An associated circuit stores or registers the paging signal. When the switch is returned to its normal position, the audible sound is produced. A lamp may be included to indicate that a paging signal is received.

Abstract: A radio receiver is provided with a local oscillator whose frequency is switched so that the receiver is normally receptive to the stronger signal but so that the receiver is momentarily and periodically made receptive to the other weaker signal. A circuit compares the relative strengths of the two signals, and if the weaker signal becomes stronger than the previously stronger signal, then reception is switched to the now stronger signal with momentary and periodic reception of the now weaker signal. Thus, interference-free and good reception of the transmitted information is provided.

Abstract: First and second bands of separate frequencies are coupled through hybrid transformers and frequency isolation filters to each of three phase wires of a power transmission line. The hybrid transformers and filters are arranged so that both bands of frequencies are transmitted and received even though there is an open or short circuit on one of the feed lines or one of the phase wires, thus providing the reliability desired or needed, particularly when the frequency bands provide relaying functions.

Abstract: A process treats a normally hydrophobic polymeric surface with a special phosphoric acid composition having a P.sub.2 O.sub. 5 concentration of 70-82% to make the polymeric surface hydrophilic and thus receptive to metal coatings. The process is especially suitable for surfaces of fluorocarbon polymers, such as tetrafluoroethylene and trifluorochloroethylene, and copolymers of tetrafluoroethylene and hexafluoropropylene.

Abstract: Many radio continuous tone controlled squelch systems use a digitally generated tone. A digital adder is provided for the digital tone generator to introduce a phase shift to the tone to indicate that a radio transmission is ending.

Abstract: Binary messages received over a radio channel are subject to fading or noise degradation because of the radio channel. Accordingly, a predetermined binary preamble followed by a synchronizing word are transmitted ahead of the message. In order that the synchronization be correct, the end of the preamble should be determined as accurately as possible. This is achieved by fast and slow detectors which receive the preamble. The fast detector output is applied to a time delay. The slow detector and the time delay outputs are applied to an output circuit which produces an output signal in response to the slow detector and the time delay outputs both being present. The fast and slow detectors and the time delay are arranged so that the output signal is produced at the desired time after the preamble begins, thereby accurately indicating when the synchronizing word is to begin.

Abstract: A timer and fuse circuit are provided with a radio transmitter for blowing the fuse if the transmitter is continuously operated longer than a predetermined time. After the fuse is blown, the transmitter cannot be operated until a technician replaces the fuse. This prevents operators from causing willful interference for long periods of time, and provides means for detecting those operators who cause such interference.

Abstract: In previous power line carrier systems, the gain of a broadband frequency amplifier was controlled by a feedback loop that utilized the magnitude of a pilot frequency signal. When the amplifier was turned on or when the gain control loop was switched into the circuit, large magnitude signals in the broadband of frequencies tended to overdrive the amplifier. This condition caused the pilot frequency signal to be suppressed so that the gain of the amplifier was kept too high. As a result, the broadband signals were limited and distorted. The pilot frequency signal stayed suppressed so that the carrier system caused faulty operation. The invention provides an added feedback loop that controls the gain of the broadband frequency amplifier as a function of the broadband of frequency signals until the pilot frequency signal can control the gain. After the pilot frequency signal begins to control, the broadband frequency loop is rendered inoperative.

Abstract: In a radio communication system having a command or base station and one or more controlled stations, the base station transmits outbound binary function messages to the controlled stations in order to make an inquiry or give a command to one or all of the controlled stations. The controlled station responds with an inbound binary message. The outbound messages comprise a sequence of binary bits at a first rate and having a first synchronizing word of nine bits, a first address word having eight message bits and four parity bits and produced three times, a second synchronizing word that is the binary inversion of the first synchronizing word, a second address word having eight message bits and four parity bits and produced three times, a third synchronizing word that is the binary inversion of the first synchronizing word, and a command word having eight message bits and four parity bits and produced three times.

Abstract: In a radio communication system having a transmitter at a first location for sending binary messages to a receiver at a second location, it is necessary that the receiver be synchronized with the binary message so that the start or beginning of the message can be accurately determined. This synchronization is provided by synchronizing words spaced in each binary message, each synchronizing word having a predetermined sequence of binary values. If a receiver receives two synchronizing words having the predetermined binary values, it produces an in-synchronization signal so that messages will be properly received. If, after the in-synchronization signal is provided, a predetermined consecutive number of synchronizing words failing to have the predetermined sequences are received, then the receiver produces an out-of-synchronization signal. The in-synchronization and out-of-synchronization signals provide reliable operation of receivers which receive binary messages.

Abstract: In radio communication systems transmitting voice and data, data is frequently transmitted at the beginning of the transmission, and this may then be followed by voice. The sound of the data in the receiver loudspeaker is unnecessary and often annoying. This sound is eliminated by a muting circuit which initially mutes the receiver for a predetermined time following receipt of a carrier signal, and then mutes the receiver when data is detected. After the data ends, the receiver is unmuted if a carrier is still present.

Abstract: Relates to a composition and method for cleaning and coating metal surfaces comprising a mineral acid, a phosphoric acid concentrate having a P.sub.2 0.sub. 5 content of about 72-80% formed by heating 54% phosphoric acid with a mono- or polysaccharide, a dibasic acid such as succinic acid, thiourea and a wetting agent.

Abstract: A plurality of transmitters, such as radio transmitters, frequently share a common communication medium or path, such as a single radio frequency channel. In order to prevent two transmitters from simultaneously transmitting over the common medium, each transmitter is provided with control apparatus. This apparatus causes transmission in response to a start action and in the absence of any other transmission on the medium. The apparatus also produces a repeating signal at predetermined intervals in response to the start action, so that if there is a transmission on the medium, the repeating signal continues until such time as there is an absence of any transmission on the medium. The repeating signal then causes a transmission, and thereafter the repeating signal is stopped. The interval between repeating signals may be the same for each transmitter, but simultaneous transmission by two transmitters will not or is very unlikely to occur because start times are likely to be different.

Abstract: In a radio communication system having a command or base station and one or more controlled or mobile stations, the base station continuously transmits outbound function messages in binary bit form to the mobile stations. Each outbound function message comprises a sequence of binary bits forming a first synchronizing word, a first address word transmitted three times, a second inverted synchronizing word, a second address word transmitted three times, a third inverted synchronizing word, and a command word transmitted three times. All mobile stations receive the outbound messages and synchronize on them, but only that mobile station whose address is transmitted responds. Each mobile station is synchronized when it properly receives two consecutive synchronizing words in sequence, and remains in synchronization unless five consecutive synchronizing word errors occur. The response from the mobile station to the base station is an inbound message also in binary bit form.

Abstract: Apparatus is provided for measuring the resonant frequency and the coefficient of coupling of a plurality of coupled piezoelectric resonators. A plurality of electrode terminals are provided in the apparatus for connection to respective resonator electrodes, and a common terminal is provided for connection to common electrodes of the resonators. First switching means are connected to a signal source for applying the signal selectively to one of the electrode terminals. A parallel resonant circuit is coupled between each of the electrode terminals and the common terminal respectively to provide a relatively high impedance at the resonant frequency of the adjacent resonators. Second switching means are connected in parallel with the parallel resonant circuits for selectively short-circuiting the resonant circuits.