Abstract: A headphone having a pair of microphone-loudspeaker units interconnected by a clamping strap for holding the units against the ears of a wearer. The loudspeaker and a microphone of each unit are isolated acoustically from each other by an enclosure. The enclosure is formed with a generally semicylindrical surfaced portion to simulate the human earlap and a flat surface normal to the semicylindrical surface. The microphone is mounted on the flat surface with its main direction of acoustic sensitivity oriented to a dummy earlap to receive a sound wave reflected therefrom.

Abstract: A head gear assembly including first and second sound attenuating earcups and means for supporting the earcups over the ears of a wearer and in which each of said earcups has an earphone therein, one of said earcups has a contact microphone therein and switch means is provided for enabling said contact microphone while disabling the earphone in the cup in which the contact microphone is located.

Abstract: A system is disclosed for providing emergency announcements to telephone subscribers when a group of communication paths is out-of-service. More specifically, one operative communication path extending from a base location to a remote location is connected at the remote location to a plurality of out-of-service or dead communication paths also extending from the base location to the remote location. Emergency announcements are transmitted from the base to remote locations over the selected one good path and applied to the plurality of dead paths. Subscribers are then connected at the remote location to the so-called dead paths to hear emergency announcements.

Abstract: An apparatus identifying a class of called telephone lines by extending an identity signal back over the called line to a calling central operator or control. The identifier apparatus includes a signal identity generator connected to the called line, a signal decoder located at a calling central control such as an operator cordboard or traffic service position (TSPS), and a time-out for deactivating the generator after a predetermined time period has elapsed. A method is also set forth where a uniquely coded signal is extended over the communication line to an operator when an "OFF HOOK" condition appears from the called line to warn the operator that the called line is not authorized to receive collect calls.

Abstract: Described herein is a system for automatically providing interconnections among a plurality of telephone lines serving a subscriber station all under the control of a remote caller. An incoming call to the system is automatically answered, and the incoming line is then connected to an outgoing line either immediately or in response to tone or pulse dialing signals dialed in by the caller. Upon receipt of dial tone on the outgoing line the caller can dial out a call thereon directly from his remote calling location. If dial tone persists on either line for a predetermined time all lines are automatically disconnected. By dialing his own number on the outgoing line and then hanging up, the caller can have the system call him back on the outgoing line, after which he can dial in control signals on the outgoing line to reconnect it to either the original incoming line or another line to dial out calls thereon.

Abstract: In an attachment apparatus for a key telephone system of the type which permits a plurality of intercom substations to access a trunk telephone line via a common communication circuit, a novel subset operable switching circuit is disclosed that permits each subset access to said common communication circuit only on an individual one-at-a-time basis. Transistor circuitry is provided to lock out other stations when more than one subset tries to gain access at the same time.

Abstract: A protection circuit for a subscriber's telephone set which comprises a resistor applied in series with the subscriber's line to which resistor a threshold device is connected in parallel, a network being provided which comprises the control input and which is connected between the subscribers' lines while the output of the threshold device is connected to the control input to switch the normally high impedance to a low impedance when the threshold voltage of the threshold device is exceeded by the voltage across the resistor.

Abstract: An automatic telephone installation applicable to chronological call distributions including a plurality of inputs through junction units to a connection network formed of a switching circuit, a plurality of switching position stations, operator stations and outgoing junction units connected to said switching circuit and the outputs of which constitute the outputs of said installation, and a central processor comprising a memory with a stored program. The installation permits a flexible operation namely for reservation purposes together with a printing of all useful statistical data.

Abstract: A stereo speaker system with two spaced-apart speaker housings is adapted for mounting on the backrest of a chair by attachment thereto with a universal, adjustable mounting bracket. Each speaker housing is adjustably supported on opposite sides of the space occupied by a person's head while sitting in the chair by a support arm adjustably connected to the speaker housing on one end and adjustably connected to the mounting bracket on the opposite end. The mounting bracket has downwardly extending members for gripping the front and rear surfaces of the chair backrest, the space between the front gripping members and the rear gripping members being adustable for removable mounting on the chair and for mounting on a variety of chairs with varying sizes of backrests.

Abstract: Hybridless bidirectional transmission networks typically include telephone line coupling transformers and unidirectional amplifiers for enhancing outgoing and incoming signals. Unwanted signal components in the outgoing direction, caused by cross coupling via the transformer of incoming signals, are minimized by employing a canceller network in circuit with the incoming and outgoing amplifiers. The canceller network has a complex transfer characteristic to compensate substantially for complex impedance components of the coupling transformer and 2-wire transmission facility and to generate a signal which is substantially a replica of the unwanted outgoing signal components. The replica signal and unwanted signal components are algebraically combined in the outgoing amplifier effectively to eliminate the unwanted signal components from the outgoing path.

Abstract: The present invention relates to a stethoscope, more particularly to a two-way stethoscope which permits hearing both direct and amplified sound from the human body through manipulation of a simple switching means at hand. The microphone for the electronic mode is located in the chestpiece, while the earpieces contain the speakers.

Abstract: For use in telephone answering service installations, a circuit device is disclosed for bridging or patching external calls, such as an incoming call to a dialed-out call, and for timing the duration of (actual time usage of) the interconnection. The device is adapted for providing a coupling between a pair of the telephone front cord plugs of a conventional PBX switchboard. Circuitry is provided for sensing the mechanical connection of a jack to a plug and for sensing electrically the completion of the telephone call connection, for inductively coupling incoming and outgoing calls, for automatically disconnecting the inductive coupling upon sensing termination of a call connection and for timing, displaying and at least temporarily storing the duration of the call interconnection for entering a time charge to the customer's account.

Abstract: An apparatus for transmitting the wearer's voice is mounted inside a breathing mask and includes a microphone and a protective sheath substantially encasing the microphone. The protective sheath includes a thin, pliable wall which is kept in contact with the sensing diaphragm of the microphone so that, when the wearer speaks and sets the sheath wall into vibration, the vibration is directly communicated to the microphone diaphragm. In one illustrative embodiment, the sheath is formed as an integral, continuous pocket in the mask body which extends inside the mask and has an opening out of the mask.

Abstract: An automatic dialer adapted to efficiently blend the capabilities of an automatic answering machine and a central paging system wherein the automatic dialer detects messages left with the answering machine and in response thereto dials the central paging system, gains access thereto, dials the pre-programmed number of a pager, causing the central paging system to immediately page the user. The automatic dialer page assures that the proper information is conveyed to the central paging system, continuing to recycle internal calling circuitry until the call has been properly completed.

Abstract: A line circuit for a key telephone system using three relays, a line relay, a ring relay and a combined off-hook and hold relay. To control the energization of the ring relay and the off-hook and hold relay responsive to inputs from the exchange or from a station of the line, an operational amplifier network is used. Two amplifiers are used as individual relay drivers and two are used as comparators. The amplifiers of this network may be identical circuits as part of a quad circuit chip. On a ring signal from the exchange, a ring comparator amplifier is activated to energize the ring relay. On a station of the line going off-hook, the off-hook driver amplifier is activated directly to energize its relay. When a station of the line goes into hold, the off-hook and the hold comparator amplifier is activated to energize both the ring relay and the off-hook relay. The line relay is energized during only the ring and hold conditions, and is shunted against energization during the off-hook condition.

Abstract: A combination acoustic and electronic stethoscope which can be operated with one hand is disclosed. The stethoscope has a combination slide valve-electrical switch located in the chestpiece for conversion from an acoustic to an electronic mode of operation. The microphone for the electronic mode is located in the chestpiece and the speaker is located in the Y connector of the earpieces. A volume control and frequency selector control are operative in the electronic mode.

Abstract: A headphone earpiece for wearing on a person's ear, comprises an annular pad adapted to engage around the ear and a sound transducer having a transducer diaphragm supported within said pad so as to define a coupling space between the transducer diaphragm and the person's ear. The support means includes a rigid plate between the diaphragm and the pad which has frictional resistances distributed thereover and which may advantageously comprise the material of the plate itself or a plurality of openings or holes having acoustic frictional resistance elements therebehind or positioned in the holes. The rear portion of the support means includes a cap having perforations which covers the back portion of the transducer.

Abstract: A personal audio listening system to be worn by an individual listener is disclosed and includes a pair of speakers mounted within a flexible supporting body which surrounds the back and side portions of the listener's neck. The supporting body may include portions which extend generally forward from both sides of the listener's neck and may be joined by a safety releasable fastener to form a closed loop around the listener's neck. The supporting body includes acoustical and safety padding, speaker grills for protecting the speaker cones and the necessary electrical connections for coupling to an audio signal source. The audio signal source may be external to the supporting body or may be enclosed within the supporting body.

Abstract: Automatic communication establishment between two telephone subscribers of different exchanges. The identities of the caller and the called are transferred to the called exchange in the event that the called line is busy, permitting disconnection of the two exchanges. The called's line is thereafter monitored until becoming free upon which the caller's identity is utilized by the called's exchange for calling back the caller. If the caller's line is now busy, the transfer of the called and the caller's identities take place again, this time back to the caller's exchange. The caller's line is similarly monitored until free, after which the method is repeated until communication is established.A separate embodiment includes the step of testing whether the called party does not reply. Identities are transferred to the called's exchange for awaiting an indication that the called party has returned. The return of the called party initiates the call-back method for establishing communication.

Abstract: A system for monitoring respiratory pressure or other pressure-variable function at a remote location develops within a transmitter terminal a carrier tone frequency-modulated according to applied pressure. The carrier tone is conveyed over a conventional telephone channel to a receiver terminal wherein an analog signal is developed from the carrier tone for application to recording or indicating instruments. The base frequency and deviation characteristic of the carrier tone is preset and non-user adjustable to avoid the necessity of setting up the system prior to use. To assure system continuity a pilot tone is generated at the receiver terminal and conveyed over the telephone channel to the transmitter terminal, and an alarm is sounded at the terminals when either but not both of the pilot and carrier tones are absent in the telephone channel. The terminals are preferably constructed within compact housings having wells for receiving the handsets of associated telephones for convenience of use.