Abstract: An apparatus for measuring the distance between an outwardly extending planar surface on a head space gauge and a planar surface surrounding the head space gauge on the barrel of a gun. This distance is used to calculate the head space of a gun. A housing is provided for abutment with the planar surface on the barrel and has an opening for receiving a sleeve of a dial indicator. A set screw arrangement is provided for securely holding the sleeve of the dial indicator in a desired relationship for the measurement process.

Abstract: A hearing aid that generally provides greater amplification for speech signals than noise signals. The hearing aid includes a microphone, variable highpass filter, transducer, and sensor assembly. The sensor assembly detects the amplitude of a band of low frequencies of the highpass filtered microphone signal, and provides a feedback signal to the variable filter to influence its cutoff frequency based on the characterisics of the highpass filtered microphone signal. The sensor also takes the time characteristics of the signal envelope into account, distinguishing between steady state noise-like signals and dynamically varying signals, such as speech. In response to loud, low frequency, substantially steady state signals, above a threshold amplitude, the sensor provides a feedback signal to the variable filter such that the cutoff frequency is raised.

Abstract: A fire suppression fitting for mounting a conduit extending through an opening in a supporting surface. The fitting includes a main body with threaded ends and a longitudinally disposed bore. The conduit is slideably received through the bore. The fitting further includes a gasket, a lock washer and an anchoring nut. The anchoring nut secures the main body on the supporting surface and the gasket in sealing engagement around the supporting surface opening. The coupling further includes a compression nut and a compression gasket, the compression nut selectively urges the compression gasket into sealing fire impeding relation around the conduit.

Abstract: A high efficiency amplifier circuit includes first and second modulator circuits. The output waveform from the first modulator is modulated by the input electrical signal to be amplified. The output waveform from the second modulator is simultaneously modulated with an inverted representation of the input electrical signal. Outputs from the two modulator circuits are coupled to a push-pull output bridge. The load is coupled across first and second output terminals of the bridge such that a tri-level output representation of the amplified input signal is applied thereto.

Abstract: A bias current compensator to supply the input bias current of a transistor. The bias current compensator may be used, for example, with the controlled amplifiers used in an automatic gain control system. The bias current compensator prevents bias current changes, caused by a varying control signal, from appearing in the output of the controlled amplifier. The bias current compensator includes a current source, first, second, and third transistors, and a feedback amplifier.

Abstract: A hearing aid that is compact and efficient and that provides a high degree of control over its frequency response and also over its output level versus input level characteristic. The frequency response control includes an adjustable four pole high pass filter and an adjustable four pole low pass filter, to define the pass band, and an adjustable slope filter, to define the slope within the pass band. The control over the output level versus input level characteristic includes an input AGC system with well defined, independent control of compression threshold and compression ratio, an adjustable peak clipper, and a selectable output AGC system that tracks the peak clipper setting.

Abstract: A hearing aid that is compact and efficient and that provides a high degree of control over its frequency response and also over its output level versus input level characteristic. The frequency response control includes an adjustable four pole high pass filter and an adjustable four pole low pass filter, to define the pass band, and an adjustable slope filter, to define the slope within the pass band. The control over the output level versus input level characteristic includes an input AGC system with well defined, independent control of compression threshold and compression ratio, an adjustable peak clipper, and a selectable output AGC system that tracks the peak clipper setting.

Abstract: A differential voltage threshold detector that may be used in a hearing aid circuit. The configuration includes an inherent differential/full wave operation, without the need for additional circuitry. The detector includes a differential transconductance stage, first and second "top" current mirrors (which respond to the transconductance stage), first and second "bottom" current mirrors (which respond to the top current mirrors) and a detector (which responds to the current levels in the mirrors). The detector effectively issues an output signal when the voltage applied to the threshold detector varies by more than a predetermined amount.

Abstract: A voltage regulator for producing first and second reference voltages. The regulator includes first and second transistors, of a first polarity, having coupled emitters, and third and fourth transistors, of a second polarity, having coupled emitters. A first amplifier is driven by the collectors of the second and third transistors, and provides a signal to the bases of the third and fourth transistors. A fifth transistor, of the first polarity, has its collector interconnected to the base of the second transistor, and the emitter of which is interconnected to the emitter of the first and second transistors. A second amplifier is driven by the collectors of the first and fourth transistors, and provides a signal to the bases of the first and fifth transistors. The wiper arm of a variable resistance whose end terminals are connected between the base and collector of the fifth transistor provides an adjustable reference voltage output over the range of the first and second reference voltages.

Abstract: A current source provides an output current that is substantially exponentially related to a difference between input voltages. The output current is also substantially linearly related to an input current. The current source includes first, second and third transistors interconnected to one another. The basic current source may be used as a "building block" to produce more complex control functions.

Abstract: An improved compansion system that more effectively increases the dynamic range of other circuit elements. The system includes both a compression circuit to limit the input signal amplitude for a circuit element, such as a filter, and an expansion circuit to receive and modify the output of the circuit element. The expansion circuit restores a substantially linear input-output amplitude relationship and may prevent substantial overloading in the circuit element, thereby increasing the dynamic range of the circuit element.

Abstract: A hearing aid that is compact and efficient and that provides a high degree of control over its frequency response and also over its output level versus input level characteristic. The frequency response control includes an adjustable four pole high pass filter and an adjustable four pole low pass filter, to define the pass band, and an adjustable slope filter, to define the slope within the pass band. The control over the output level versus input level characteristic includes an input AGC system with well defined, independent control of compression threshold and compression ratio, an adjustable peak clipper, and a selectable output AGC system that tracks the peak clipper setting.

Abstract: A key base or carrier permits a user to attach any off-the-shelf integrated circuit chip in dual in-line packages (DIP) thereto to form a switch-like device merely by bending the chip leads around the edges of the carrier. The carrier, with chip attached, is inserted into a housing between the rows of posts of a standard wire wrap socket and is rotated 90.degree. after insertion to wipe the bent chip leads on the socket posts to insure good electrical contact to the posts. The socket portion of the wire wrap socket assembly can then be used to plug in a ribbon cable, fitted with DIP headers (plugs) on each end, to transfer the electrical connections of the chip to the product circuit board. An independent switch, affixed to the wire wrap socket housing and actuated by the chip carrier, after all connections are made, signals the user's circuit that the chip is in place.

Abstract: A key device carries an integrated circuit chip or dual in-line package (DIP) and permits connecting the chip into a circuit board such as a logic circuit board of a computer terminal, from an exterior opening of the housing or cabinet carrying such circuit board. The key device connects any desired chip electrically to spring contacts of a socket located in alignment with the exterior opening. The socket in turn is connected through a ribbon cable for example to a connector on the circuit board at some desired location within the housing. The chip carrying key device is rotated 90.degree. after insertion to insure good electrical contact. When the key is to be removed, the key device is rotated 90.degree. to a position where it is electrically disconnected from the socket leads and can be removed from the housing. The chip can be reprogrammed if desired.

Abstract: A fire protection sprinkler head arrangement comprises a flange attached to a bracket on the sprinkler body by boss and shoulder joints, e.g., bayonet joints. The flange serves as a brace preventing sagging of ceiling tile and unwanted retraction of the sprinkler head rearwardly with respect to the ceiling or a sidewall. One embodiment of the flange is adjustable axially relative to the sprinkler body by an upwardly directed series of shoulder joints into which the boss is selectively fitted to conform to a particular ceiling or wall structure and feeder pipe system.

Abstract: An adjustable drop nipple for sprinkler heads is disclosed which comprises a stationarily mounted collar with internal threads that receives an externally threaded nipple, and whereupon rotating the nipple a portion of its length is caused to retract into the collar or extend from it, depending on the direction of rotation, in order to precisely regulate vertical elevation of a sprinkler head attached to the lower end of the nipple. An effective seal against leakage of water is achieved by use of one or more O-rings on the nipple which abut a smooth bore section inside the collar.

Abstract: A sprinkler is disclosed which comprises a flange attached to a bracket on the sprinkler body by means of boss and shoulder joints, e.g. bayonet joints. The flange can serve as a bracing means which prevents sagging of ceiling tile or unwanted retraction of the sprinkler head rearward of an opening in a sidewall. When used with recessed sprinklers, a cover plate can be attached to the flange with a bonding material having a low softening point. By means of the boss and shoulder joints, the flange and the attached cover plate can be easily mounted on the sprinkler as a subassembly, and can be just as easily removed therefrom for inspection and/or servicing of the sprinkler.

Abstract: A device for heating a room or building thermostat by radiant means or a combination of conduction, convection and radiation in such a manner as to cause localized thermal energy in the vicinity of the thermostat. The temperature of the area controlled by the thermostat is thus caused to be reduced by an amount approximately equal to the rise in temperature in the vicinity of the thermostat. The heater, as shown a small light bulb, is switched on by a timer for the time period during which the building or room temperature is to be reduced. The light is turned off when the area temperature is returned to the thermostat setting.

Abstract: A concealed, flush mounted sprinkler is disclosed which comprises a slidable deflector which, in the event of fire, is extended to an operating position by means of a compressed spring. The nozzle, a thermally responsive element, and the deflector of the sprinkler reside within a receptacle having an outer cover against which the deflector is continuously pressured by means of the spring. The cover is attached to the receptacle by means of a fusible eutectic alloy, and as the alloy begins to soften and become elastic during a fire, the compressed spring aids detachment of the cover from the receptacle while simultaneously sliding the deflector to an operating position beyond the ceiling or sidewall in which the sprinkler is mounted.

Abstract: An adjustable drop nipple is disclosed for installing fire protection sprinkler systems which comprise sprinkler head assemblies of the dry, pendant type. The downwardly extending length of a drop nipple having a sprinkler head thereon is adjusted by sliding the nipple axially in a collet having an externally tapered section that engages an internally tapered section of a stationary collet holder. When a selected drop length has been established, the collet is then compressed axially against the collet holder with tightening means whereby the nipple is firmly gripped by the collet so that axial sliding thereof is prevented, thereby maintaining the nipple at the selected drop length.