Abstract: An electret transducer comprising a diaphragm (3) arranged between first (1 or 1') and second electrodes with at least one electrode (2) arranged at some distance from the diaphragm as a stationary electrode formed with holes (5). An air gap (4) is formed between the diaphragm (3) and said electrode (2). In the case of one air gap the air gap width d and the area A (7) enclosed by four holes which are situated nearest each other in said electrode (2) are selected so that the following equation is satisfied ##EQU1## where .eta. is the dynamic viscosity of the air in the air gap. In the case of an air gap on each side of the diaphragm, the air gap widths d.sub.1 and d.sub.2 and the said areas A.sub.1 and A.sub.

Abstract: A generalized signal processing device for use as a hearing aid generates and modifies signals representative of acoustic patterns in a physiologically compatible manner which enables persons suffering from various auditory pathologies to recognize sound patterns including human speech.

Abstract: An ink jet recording apparatus has a recording liquid container storing recording liquid therein, a recording head which is supplied with the recording liquid from the container and which discharges the recording liquid to effect printing on printing paper, and a carriage on which the recording head and the recording liquid container are mounted. The recording head is secured to the carriage. The apparatus further has a recording liquid supply member having one opening connected to the recording head. The other opening of the recording liquid supply member is tightly insertable into the recording liquid container. By inserting the recording liquid supply member into the recording liquid container, the recording liquid is supplied from the recording liquid container to the recording head through the recording liquid supply member.

Abstract: The vibratable diaphragm of an electret transducer has in its central plate portion one or more formed ribs, ridges or projections resting of a substantially flat backplate. These support the active regions of the diaphragm with precise spacing from the backplate. Elongate projections can be formed to relieve membrane stresses in the diaphragm. The flexural stiffness of the diaphragm is sufficient in itself to provide mechanical stability of the diaphragm in the presence of the destabilizing forces of electrostatic attraction by the backplate.

Abstract: A method and apparatus for controlling the rotational speed and phase of a synchronous motor is provided by sensing the motion of the poles with respect to the stator to provide sensor signals. The sensor signals are converted to sensor pulses and compared to constant pulses. Driving pulses are generated so that if the poles run ahead, a braking moment is generated, and if the poles lag behind, an accelerating moment is generated.

Abstract: A stereophone includes cup assemblies which are supported over the ears of a user by a headband. Each cup assembly includes a piezoelectric acoustic transducer and a dynamic acoustic transducer. The reproduction of the entire audio spectrum is divided between the two transducers at a crossover frequency which is established by an acoustic filter.

Abstract: A two stage positive shift starter drive system for an internal combustion engine is disclosed. A pair of electrical switches are sequentially actuated by an actuator solenoid engaging the starter drive's pinion gear with the engine's ring gear. The first switch actuated after a predetermined displacement of the solenoid's armature applies electrical power to the cranking motor through a resistance connected in series with the cranking motor and connected in parallel with the solenoid pull-in coil. The resistance reduces the electrical power applied to the cranking motor and the potential across the solenoid pull-in coil thereby reducing the rotational speed and the engagement force applied to the pinion gear. The end of the armature travel closes the second switch applying full power to the cranking motor permitting normal cranking of the engine with the pinion gear fully engaged with the ring gear.

Abstract: The present invention relates to 1+1 type carrier telephone transmission systems for connecting two subscriber terminals to a telephone exchange via a common two-wire link, one of the terminals being connected via the conventional audio channel, and the other terminal being connected by a channel referred to as a super-audio channel. Disturbances caused in the super-audio channel by signalling, dialling and calling signals of the audio channel are reduced by inserting a current-limiting two-port network in series in the audio channel and at the exchange end of the 1+1 system, in between the filter which separates out the audio channel and the rest of the exchange. Advantageously, an interference limiting low-pass filter (50) is also placed in series on the audio circuit. It has a capacitive shunt arm with a mid point connected to exchange battery ground.

Abstract: A four-wire termination circuit has a series arrangement of a current source controlled by a transmitting arm of a four-wire line and a first resistor. This arrangement is connected in parallel to a two-wire line terminal impedance formed by a second resistor and an impedance. The terminal impedance terminates the two-wire line in reflection-free fashion. Voltages dependent upon a transmitted signal current which are equal in value but opposed in phase appear across the first and second resistors. A voltage which is dependent upon a received signal current from the two-wire line appears across the second resistor. In a receiving arm of the four-wire line, an intermediate value voltage is present which is independent of the transmitted signal in the transmitting arm.

Abstract: A bistable switch for controlling a latching relay for connecting and disconnecting an air conditioning load, operable over a telephone line by the application of a short burst of one of a pair of determined frequencies. The switch includes a power supply capacitor (35) charged directly from the telephone line (32, 33). A pair of narrow band filters (39, 40) each respond to one of the pair of frequencies. The output of each filter drives an FET amplifier (60) which in turn drives a charge pump (68, 69). When a sufficient amount of charge is received, the charge pump will provide a firing pulse to one of a pair of SCRs (77). The SCRs are each connected in one leg of a bridge circuit which includes one of a pair of diodes (79). The remaining legs of the bridge are formed by a pair of transistors (80) with the coil (46) of a bistable relay (47) attached across the bridge.

Abstract: A method of reducing the adaption time needed to adapt a synthetically generated secondary waveform so that it nulls a primary repetitive waveform (e.g. noise) from a source (1) of vibration, the secondary waveform generation (5) being synchronized by the source (1). The clarity and/or the amplitude of at least a part of the signal resulting from interaction between the primary and secondary waveforms is sensed (6) and used (7, 8) to reshape the secondary waveform. The invention finds application in the cancelling of repetitive vibrations (e.g. in quietening the driving cab of a vehicle).

Abstract: The present invention is directed to a means of alerting a distant party through a telephone call and a predetermined alarm that a distressed party has activated a distress button. The distressed party indicates an emergency and summons help by pressing a pad button or by means of a remote transmitter without actually going to a telephone. The transmitter signals a receiver by means of a radio frequency and triggers the receiver so that a predetermined telephone number is dialed and an emergency alert is placed on the line for a predetermined amount of time. After an additional period for verification of any emergency, the time sequence is repeated.

Abstract: An electro-optical isolator circuit especially adapted for operation in a modem which is powered solely from the telephone line and employed to isolate the line from utilization equipment. The isolator includes a guard circuit which substantially improves low current operating speed such that an inexpensive electro-optical component can be utilized at very low drive levels to achieve response times less than 10 microseconds.

Abstract: Ink jet head and method for manufacturing the same, wherein a groove or grooves to constitute ink flow path are formed in a layer of a photosensitive composition placed on one surface of a substrate.

Abstract: This invention relates to a device which permits to transmit and to receive signals through a telephone line by means of an electromagnetic linking brought about in correspondence with at least one inductive element of a telephone set, without any necessity of interrupting the line which feeds the set concerned.

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: A hybrid circuit includes a capacitive charge-transfer arrangement, comprising parallel capacitors and series switches,for coupling signals in one or both directions between a four-wire line and a two-wire line. The switches are constituted by VMOS power FETs. In one embodiment, the charge-transfer arrangement is provided in the receive path to give the desired properties of electrical isolation and unbalanced to balanced conversion of receive path signals. Signals from the two-wire line are coupled to a transmit path of the four-wire line via an attenuating and high-pass filtering arrangement and a differential amplifier, thereby providing good common mode rejection of high voltage signals, especially at power line frequencies. In another embodiment, the charge-transfer arrangement is provided, commonly for the receive and transmit paths, for coupling the two-wire line to the remainder of the hybrid circuit.

Abstract: A telephone music device adapted to be inserted within the hollow portion of a telephone handset. The device draws power directly from the telephone line and requires no external power supply. When the handset is in a upright position, as normally utilized for a conversation, the telephone music device is electrically disconnected from the telephone circuit. However, when the handset is laid down such as on a table, the telephone music device becomes electrically interconnected with the telephone circuit. It draws power therefrom and generates a musical melody which is coupled to the telephone line. Alternate embodiments can be clipped to the handset or base of a modular telephone.

Abstract: An automatic answering device controlled by attached data equipment and used with a modem powered from the telephone line. The modem and automatic answering device are automatically connected to and subsequently powered by the telephone line when a ring signal has occurred on the telephone line and the data equipment has indicated that it is ready to receive data. The energy needed to connect the modem to the telephone line is slowly accumulated from a data equipment over a period of time prior to the connection of the modem to the telephone line. The modem automatically hangs up when the local data equipment signals disconnect or the modem at the other end of the telephone line disconnects.

Abstract: A narrow-frequency band, acoustic transducer of high conversion efficiency over a narrow-frequency band, which transducer comprises: a truncated diaphragm having a depressed, circular area and a peripheral edge about the circular area and a convex cap section extending outwardly from the circular area; a vibration board adhesively secured about the peripheral edge of the diaphragm, to couple acoustically the vibration board to the diaphragm on one side; and a piezoelectric element centrally secured to the other side of the vibration board, with electrical leads to the piezoelectric element, whereby electrical energy input to the piezoelectric element provides a high decibel acoustical output about the natural resonance frequency of the vibration board.