Abstract: Signal transmission apparatus is provided for a communications system having a plurality of transmitters for transmitting information signals over any one of several transmission channels, and further having a plurality of receivers for receiving the information signals over any one of the transmission channels. In order to establish a selected transmission channel between a particular transmitter and a particular receiver, the transmitter selects an unoccupied transmission channel and transmits thereon a code identifying the receiver using a wide band signal for high speed bit transmission. When the receiver detects the presence of the identifying code over a particular channel, it first determines that the transmitter is the particular transmitter and, if so, establishes the transmission channel therebetween.

Abstract: This microphone includes a microphone element, speaker and antenna all internal to the microphone housing. These components are carried by a chassis that is fastened to the microphone body at its lower end which also provides the effective attachment point for the microphone cable. The speaker is mounted in the chassis at an angle having its face slight upwardly incline to project sound towards the top of the microphone. An antenna element includes walls on either side of the speaker for reflecting sound upwardly. The antenna element has apertures in its top portion to allow for the passage of sound therethrough. The microphone element is also in a position for picking up sound through the top of the microphone.

Abstract: A ringing detection circuit for accurately detecting a ringing having opposite polarities which arrive over a telephone subscriber's line. After the detection of the fact that the AC waveform of the ringing has reached a predetermined level in one of the polarities, variations in the waveform in that polarity are neglected until the waveform reaches a predetermined level in the other polarity. This allows a ringing to be detected with accuracy without responding to distortions of the ringing.

Abstract: When a floating battery feed circuit is used to power telephone lines, it is desirable to provide an anti-corrosion biasing circuit to keep the voltage on the tip and ring conductors from becoming positive. This can be done using an anit-corrosion circuit that sinks a dynamic amount of current from the tip conductor. A line circuit including such biasing is, however, incompatible with special lines such as PBX lines that rely on a grounded tip conductor in the talk state. In accordance with the present invention, a constant current is supplied from a ground reference circuit to the ring conductor of such special lines only when loop current is flowing. The magnitude of this supplied current is such that the anti-corrosion circuit holds the tip conductor sufficiently close to ground potential to allow the proper operation of circuits connected to the special lines.

Abstract: A telephone cord twist restrainer which is comprised of a rudder-like plate which is attached to a coiled telephone cord by means of slotted holes formed in the plate and by two (2) projections extending from the plate which slidably fit, in opposing directions, within the coils of the telephone cord. The plate extends laterally on a single side beyond the diameter of the coils in lengthwise orientation with the coiled cord, where its extending mass provides stability to the coiled telephone cord both through physical contact at nearby surfaces, and by the location of weight of the plate itself outside of the periphery of the coiled telephone cord. Notches may be formed on the projections so as to provide improved retention within the coiled cord, especially when the coiled telephone cord is extended and stretched out close to its maximum limit.

Abstract: This arrangement is intended to control the operation of the coefficients adjusting circuit (12) of an echo canceller and of the operation of a center clipper (15) inserted in the send path (7) of a four-wire circuit at the output of the subtractor (13) of the echo canceller for suppressing there, when it is set to its active state, the signals whose amplitude is lower than or equal to a clipping threshold. The control arrangement operates on the basis of the signal in the receive path (2) of the four-wire circuit, the level N.sub.REC of this signal and the levels N.sub.AV and N.sub.AP of the signals before and after the subtractor (13). It comprises a controller (21) for comparing the level N.sub.AV to two fixed thresholds N.sub.AV0, N.sub.AV1 and for comparing the ratio N.sub.AP /N.sub.AV to a threshold a which is capable of varying as a function of N.sub.AV, the center clipper being only set to its active state when the level N.sub.AV is comprised between N.sub.AV0 and N.sub.AV1 and the ratio N.sub.AP /N.

Abstract: A touch sensitive electronic volume control circuit so that the gain of an amplifier can be changed to any level from zero to maximum and the gain can be retained for periods of time without user adjustment or for power supply replacement.

Abstract: An apparatus for indicating to a central service unit of a telephone system having a central service unit coupled to a plurality of station sets whether a particular station set comprises a speakerphone and the type of speakerphone from among two types of speakerphone, is disclosed. The station set includes a microprocessor controller having an input line coupled to a selected one of a low or high logic level. The input line is connected to an electronic switch which receives interrogation signals from the central service unit. Depending on the logic level to which the input line is coupled and the state of the switch, the central service unit can determine whether the station set comprises a speakerphone and the type of speakerphone.

Abstract: A high-speed modem that transmits and receives digital data on an ensemble of carrier frequencies spanning the usable band of a dial-up telephone line. The modem includes a system for variably allocating data and power among the carriers to compensate for equivalent noise and to maximize the data rate. Additionally, systems for eliminating the need for an equalization network, for adaptively allocating control of a channel, and for tracking variations in line parameters are disclosed.

Abstract: First and second output signals are taken from a floating element in a CCD charge transfer channel and from the terminal drain diffusion of that CCD charge transfer channel. The floating element is part of an electrometer, and the electrometer response is wide-band sampled at the CCD charge transfer channel clocking rate. Current flow through the terminal drain diffusion is sensed by the input circuit of a low l/f noise transresistance amplifier. Continuous-frequency-spectrum low-noise output signal is generated from the low-frequency components of the transresistance amplifier response and from the high-frequency components of the processed second output signal. Subsequent filtering removes unwanted clock and aliased frequency components.

Abstract: Insert earphones, which are especially useful for audiometry applications include a transducer which is coupled to a resonance cancellation tube as well as to a main tube which is coupled to the ear, with series acoustic dampers in the tubes, operating in a known manner to obtain a smoothly varying frequency response characteristic. An electrical equalization network is coupled to the transducer, cooperating with the acoustic components to obtain a frequency response characteristic which is either flat or which matches that of the human ear. The dampers in series with the main and cancellation tubes have acoustic resistances which are respectively about 20% lower and 20% higher than the characteristic impedances of such tubes, operating to obtain a broadband increase in output.

Abstract: Response-modifying acoustic couplers are provided for use between an output port of a hearing aid unit and an earmold at the entrance to the ear of a wearer, including a passage and a chamber which respectively provide a high acoustic inertance and a high acoustic compliance to cooperate with other acoustic elements and to form an acoustic network producing a predetermined frequency response characteristic.

Abstract: An adapter for a cellular mobile phone unit which converts the unit to include a plurality of telephone numbers. A main circuit board is coupled to a microprocessor of the unit, which board includes a plurality of number assignment modules, or NAM's (ROM's), each NAM having its own unique telephone number code. The NAM's are connected such that fifteen of the sixteen pin-connections of each NAM are correspondingly and respectively connected in series, for coupling to the fifteen pin-connections of a plug at one end of a ribbon cable, the other end of the ribbon cable being coupled to the microprocessor of the unit via the conventional NAM connection therefor. Each remaining pin of each NAM, which is not connected in series, is connected to a unique stop of a multi-position switch, so that a selected one of the NAM's may be coupled to the microprocessor in order to change the telephone number from one to another.

Abstract: An active acoustic attenuation system (2) is provided for attenuating an undesirable output acoustic wave by introducing a cancelling acoustic wave from an omnidirectional speaker (14) at the output (8), and for adaptively compensating for feedback from the speaker (14) to the input (6) for both broad band and narrow band acoustic waves, without pre-training. The feedback path (20) is modeled with a single filter model (40) adaptively modeling the acoustic system (4) on-line without dedicated off-line pre-training, and also adaptively modeling the feedback path (20) from the speaker (14) to the input microphone (10) on-line for both broad band and narrow band acoustic waves without dedicated off-line pre-training, and outputting a correction signal to the speaker (14) to introduce a cancelling acoustic wave.

Abstract: A cordless telephone having a base unit with automatic telephone answering function and a portable unit has an engaging means for forming an engaging circuit upon an incoming call from a calling party, when the portable unit is kept in the off-hook state over a preset period of time during sending of outgoing message from the base unit, and an outgoing message inhibiting circuit which activated by output of preset timer means and inhibit outgoing message then both parties' conversation can be recorded in recording means on base unit which is set in stand-by mode.

Abstract: An active acoustic attenuation system is provided that actively models direct and feedback paths as well as characteristics of the secondary cancelling sound source and the error path on an on-line basis. The primary model uses a recursive least mean squares RLMS algorithm that is excited by the input acoustic noise and uses the residual acoustic noise as an error signal. The secondary sound source or cancelling speaker and the error path are modeled by a second algorithm, particularly an LMS algorithm, that uses an additional auxiliary low level, random, uncorrelated noise source as an input signal. The resulting overall system provides excellent attenuation of narrow band and broad band noise over a relatively wide frequency range on a completely adaptive basis without directional transducers.

Abstract: An improved AC impedance matching arrangement including a first amplifier connected to a subscriber loop through the tip and ring conductors of a subscriber line circuit. The first amplifier is arranged to supply loop current to the subscriber loop through first and second resistors. Each resistor having a set DC value. A second amplifier connected to the tip and ring conductors is arranged to develop and output a signal responsive to AC signals applied to the tip and ring conductors from the subscriber loop. A feedback circuit connected to the second amplifier is arranged to receive the second amplifier output signal and develop and output to the first amplifier an impedance matching signal. The impedance matching signal raises the impedance seen by the tip and ring conductors above the set DC value of the first and second resistors.

Abstract: An apparatus and a method for reestablishing previously established settings on the controls of an audio mixer having at least one input channel and at least one output channel. The method includes the steps of transmitting a first test signal through the at least one input channel; measuring and recording this first test signal during a first period of time at at least one output channel; transmitting a second test signal, substantially identical to the first test signal, through the at least one input channel during a second period of time; comparing this second test signal at the at least one output during the second period of time with the recorded first test signal; and altering the settings on the controls of the audio mixer in the event that the recorded first test signal is different from the second test signal of the at least one output.

Abstract: A system for transmitting and accessing data through a standard telephone system. The system including activating a key or sequence of keys wherein each key represents a plurality of letters. Signals produced by activating the keys are compared to a data base having indexed entries of words or names. In this way, words can be input into the system using only 8 unique keys.

Abstract: An adaptive line hybrid for digital telecommunications including a bridge circuit for connection to the telecommunication line the bridge circuit having automatically adjustable components in two arms of the bridge to compensate for variations in the characteristics of the telecommunications line.