Abstract: A garment bag includes carry handles centrally disposed on the outer surface thereof and a carry strap that is snap connected to eyelets for shoulder carry. Eyelets are centrally disposed on opposite sides of the interior surface thereof and may be used for snap-hook attachment of a utility kit. A pair of bottom straps and a pair of side straps may be employed to embrace a carry-on bag that is designed to fit within the arc formed when the garment bag is folded over. The strap lengths are adjustable, and the shoulder strap used for the garment bag may be removed therefrom and attached to eyelets at each end of the carry-on bag, thus permitting shoulder carry of the carry-on bag. A compact carry-on luggage assembly is formed all of which may be tucked under a passenger seat or in an overhead compartment. Also, the units may be quickly disconnected one from the other as may be necessary.

Abstract: An echo canceller is connected in the four-wire, voice-frequency path of a communication circuit and includes an end delay analyzer which is bridged between the four-wire transmit and receive paths, and a variable delay and an echo synthesizer connected in series between the received signal path and one input of a summation circuit. The other input to the summation circuit is connected to the four-wire transmit path along which the return echo signal is propagating. Any difference appears as a residual echo at the output of the summation circuit.The end delay analyzer, in response to the received signal and the echo return signal, provides an output control signal that adjusts the variable delay to compensate for the terminal circuit delay which occurs between the echo canceller and the four-wire to two-wire hybrid.

Abstract: In a floating battery feed circuit, the voice frequency is normally connected on the subscriber loop side of the blocking capacitor which is used to prevent the DC loop current from flowing in the winding of the associated voice frequency transformer. This capacitor adversely offsets the dial pulse signals. An optical isolator is responsive to the answer control signal from a dial pulse originating (DPO) channel unit and provides a control signal to a switching circuit, which connects the voice frequency circuit to the loop during answer periods and disconnects the voice frequency circuit from the loop during dial pulse signaling.

Abstract: A detachable arm rest for a passenger seat includes a vertical member supported at one end thereof from the floor of a motor vehicle, and is adapted for attachment to the inboard side of the seat near the front edge thereof; a horizontal member extending from the other end of said vertical member, said horizontal member being adapted for connection to the back support portion of said seat, and an extension member attached to the top side of said horizontal member thereby providing a supporting surface for the interior arm.

Abstract: A floating battery feed circuit employs a single primary winding, a pulse width control circuit and a peak detector for providing a controlled current to a subscriber loop. The amplitude of the controlled current is determined by the loop resistance. A comparator circuit has one input connected to the output of a peak detector via a breakdown diode. The second comparator input is connected to a reference voltage. When the voltage from the breakdown diode exceeds a predetermined value the comparator provides an 0 output to indicate an on-hook state. For a peak detector output voltage below said predetermined value, the comparator provides a +5 volt output indicating an off-hook state.

Abstract: Differential encoding is commonly used in data transmission systems because it allows correct recovery of the data even though the polarity may have changed during transmission. However, single errors which are introduced result in double errors, i.e., error of an even number following the differential decoding process. Because many error detection schemes rely upon parity checks, which look for an odd number to determine if an error has occurred, the conversion of the single error to a double error means that single errors normally would not be detected. A precoder is used to introduce correlation by modulo two addition of the precoded present digit with a selected combination of past digits. The differential decoder will still provide double errors but a subsequent decoder, which reverses the precoding process, at least partially changes double errors into errors of an odd number.

Abstract: Under an off-hook condition a pulse width control circuit is periodically turned on by narrow pulses from a clock source. This initiates current flow from a primary dc source via the single primary winding of a transformer, and through power transistors connected in a Darlington configuration. A ramp voltage is developed across an emitter resistor of one of said power transistors and this voltage is feedback to said pulse width control circuit. When the ramp voltage reaches a predetermined value, the pulse width control circuit turns off the power transistors and the energy stored in the transformer is transferred by the collapsing magnetic field into alternating current in the secondary winding. This alternating current is rectified and filtered to provide loop current to the telephone subscriber loop. The voltage reflected from the secondary to the primary is stored in a peak detector circuit which operates to control the length of time during which the ramp voltage builds to its predetermined amplitude.

Abstract: To minimize carrier leak in the modulation of voice frequencies to the desired line frequency for a carrier system, a first balanced modulator is operated at a low frequency where low carrier-leak modulators may be constructed and a second balanced modulator, directly coupled to the first, is employed. The modulation frequency of said second modulator is very high compared to that of said low-frequency modulator. The sideband obtained from the second modulation stage is remote from said high-frequency carrier and a band-pass filter selects the desired sideband and substantially eliminates the high-frequency carrier and the other sideband. Thus, only a low amplitude of carrier leak is present which may cause interference with other channels.

Abstract: Apparatus for synchronizing the frequency of locally generated pilot signals with those of remotely generated pilot signals where frequency errors are introduced during transmission. A pair of demodulated pilot signals F1' and F2' are filtered and mixed to derive a third signal having a frequency equal to F2'-F1'. The difference frequency has no frequency error component so the third signal is used in a phase locked loop to regenerate a reference frequency (fr) signal.Two methods are disclosed to extract a control signal which is proportional to the error frequency. In one embodiment one of the received pilots (F1') is divided in frequency by 1/k1 and then subtracted from fr to yield 1/k1 times the error frequency df. By integrating this signal it becomes usable as an AFC signal to control a local oscillator.

Abstract: Two pilot signals, derived so that there is a predetermined ratio between the frequency difference of the tones and the absolute frequency of either of the pilot signals, are transmitted from a reference station to each of a number of remote stations. At each receiving station, the frequency error is derived from the frequency difference of the two pilot signals, and this frequency error is used to adjust the frequency of the local oscillator.

Abstract: An incoming bit stream is digitally processed to obtain both in-phase and quadrature-phase 7-level correlative signals. The two 7-level correlative signals are separately band limited to a passband having a bandwidth that is about 1/8th of the bit rate of the original bit stream, and these band limited signals are then separately analog modulated, respectively, using in-phase and quadrature-phase components derived from a line carrier oscillator. The modulation products are then combined in a summing circuit to derive a signal-sideband 7-level correlative signal.

Abstract: A forward error correcting digital transmission system having two separate transmission channels carrying redundant information. The signal on the first channel is encoded by combining each present bit with itself delayed m bits in time. The signal on the second channel may be encoded in the same manner only with a delay of n bits in time, or left without coding, i.e., n=0, in any case m and n are unequal integers. Both first and second channels are transmitted over separate transmission paths to the receiving terminal where each is independently decoded to obtain the original binary information from each received encoded signal.If an error is introduced into one of the channels during transmission, the encoded information necessarily contains an error in the present bit and its associated m or n delayed bit.

Abstract: RF preamplification with AGC is employed because of the wide range of signal levels to which the RF input section of a radio is subjected. A reduction in noise figure is obtained by using a single gate gallium arsenide field effect transistor (GaAs FET) as the RF preamplifier and providing an AGC control signal to vary the gain of the RF preamplifier so that the subsequent circuits are not overloaded when high RF signal levels appear at the input.

Abstract: A radio signal will often suffer from amplitude and group delay distortion caused by multipath fading. An adaptive equalizer, which effectively cancels the amplitude distortion effects, is based upon the use of control voltages derived from selected portions of the IF band; the control voltages being selectively applied to bump and slope equalizer sections to cancel the effects of amplitude distortion. Cancellation of group delay distortion is predicated upon its being proportional to amplitude of the slope correction required. Thus, group delay correction is introduced in relation to the slope correction introduced to compensate for distortion introduced during normal multipath propagation conditions.

Abstract: Deviation of a frequency modulated oscillator (FMO) is set by applying a square wave test signal to the input of the oscillator so as to generate a predetermined amount of symmetrical periodic frequency shift above and below the rest frequency, i.e., the carrier frequency of the FMO, for a desired setting of the FMO's modulation sensitivity. The FMO frequency is divided down so as to be within the range of a programmable divider in the automatic phase control circuit of the oscillator. The carrier frequency is set by program switches which are connected to an interface logic unit that provides the control information to set the divisor of the programmable divider. During testing, the square wave test signal is also applied to a control input of the interface logic unit, for adjusting the divisor so as to provide at the output a binary signal having a predetermined pulse repetition rate when the modulated signal is applied to the input to the programmable divider and the deviation is correctly set.

Abstract: A transmitter converts an incoming bit stream into a single-sideband signal for transmission over a band-limited channel such as a digital radio. The incoming bit stream is digitally processed to obtain both in-phase and quadrature-phase 3-level correlative signals. The two correlative signals are separately band limited to a passband having a bandwidth that is about one-fourth the bit rate of the original bit stream, and these band-limited signals are then separately analog modulated, respectively, using in-phase and quadrature-phase carrier frequencies which are derived from a carrier oscillator. The products from the analog modulation process are then combined in a summing circuit to derive the single-sideband signal. At the receiver, the single-sideband signal is analog demodulated using a carrier frequency that is at either end of the single-sideband frequency spectrum, i.e., C.+-.

Abstract: A DC control current is developed in a first transistor circuit and the control current is responsive to a control voltage which is proportional to the output voltage of a fixed gain amplifier. A reference voltage is applied to a second transistor which provides the normal operating bias for said fixed gain amplifier, and, also, provides a variable impedance via the diode circuit of the base-emitter junction. This diode circuit is a part of a variolossor that also includes a resistor which is connected in the series path between the signal source and the fixed gain amplifier. The bias voltage of the second transistor does not change but the diode impedance varies as the control voltage varies so as to maintain the amplifier output constant.