Abstract: The disclosed facility type determination technique ascertains whether or not a facility connection is solely digital. In the disclosed embodiments, this information is used to establish the rate at which data is coupled through the facility connection. More specifically, a predetermined test signal including a pseudorandom sequence of digital signals is transmitted through the facility or combination of facilities connecting a data source to a data destination after the connection between the source and destination is established. The received test signal is examined at the destination and the examination results are used to determine the rate at which data is subsequently transmitted between the data source and data destination. Advantageously, this technique does not restrict network facility management and can be employed in a variety of data communication applications.

Abstract: Distortion and instability due to echoes in conference communications is reduced through the use of an echo estimating filter disposed in a conference bridging circuit. This circuit includes a signal combiner which receives information signals from each of the parties in the conference communications and provides an output signal which is a combination of the received information signals and an echo compensation signal. The echo estimating filter provides this echo compensation signal in response to the combiner output signal. Advantageously, the echo estimating filter can be fixed or adaptive. In the latter case, the adaptation can be in response to the received information signals or to training sequences.

Abstract: A stored directory is searched from a display station set to obtain the telephone number of a sought-after name. The arrangement uses the station set keypad to generate signals corresponding to the spelling of the sought-after name. The arrangement adds each entry it receives to previously formed sequence of entries and, for each newly formed sequence, returns to the station set the name and telephone number contained in a directory record having a string of characters that compare to the newly formed sequence. The arrangement also provides means for scrolling through the directory.

Abstract: A gain and frequency compensated barrier circuit is disclosed for use with a telephone transmission line having variable loop lengths. A DC component of the input signal is provided to the input side of the barrier circuit. Loop length losses, as well as barrier gain variations, are adjusted on the output side of the circuit by comparing a barrier DC voltage level with a DC reference level and adjusting the AC gain in accordance therewith. Frequency response, which is also a function of loop length, is corrected by using the DC input voltage to generate an effective loop length dependent capacitor for further controlling the output signal level. An optocoupled circuit is disclosed for use in one embodiment of the disclosure.

Abstract: A two-terminal tone generating hold impedance is disclosed which is powered from a central office telephone line and provides the functions of a hold impedance in a key telephone line circuit while providing an audio tone signal to an associated telephone line when the line is placed in a hold condition. The tone generating hold impedance consists of an oscillator circuit which is self-exciting upon the application of a dc voltage resulting from the connection of the tone generating hold impedance to the telephone line. In another embodiment a line powered music receiver functions as a hold impedance and applies music, received via radio or cable transmission, to the line placed in a hold condition.

Abstract: A remote gain controlled optocoupled device is disclosed utilizing a DC reference voltage in the output section to compensate for variations in the optocoupling characteristics of the circuit. The DC voltage level output of the photodetector, which is a function of the light transfer characteristics of the circuit, is compared to a remotely controlled reference DC level. The output AC signal level, which substantially tracks the DC voltage output, is gain adjusted under control of the compared DC voltage levels.

Abstract: A modulated RF carrier signal distributing arrangement, utilizing existing line circuits, is disclosed for providing entertainment signals to key telephone lines in the active noncommunicating (hold) state. The disclosed system utilizes an existing option connector on the line circuit for connection of a music receiver circuit. A centrally located transmitter circuit frequency modulates its own RF carrier with an externally supplied music signal and is wired to the existing common dc power to distribute the modulated RF signals to the receiver via the option connector on each line circuit. The receiver circuitry demodulates the RF signal and couples the resulting music signal directly across the hold bridge leads of the associated line.

Abstract: An air controlled overhead gutter cleaner is disclosed having a head portion and a hollow supporting arm portion. The head is adapted for movement along the gutter under control of a person walking along the ground. The head is shaped such that as air, which is forced through the hollow support arm, exits from the head, leaves and other debris in the gutter are blown out of the gutter. A rear baffle is provided to deflect the expelled material forward and off the roof.

Abstract: Ringing loop-current detectors are shared by groups of telephone set line circuits. A time division switching system is disclosed having a plurality of telephone line circuits and common control circuits for switching calls over a time division communication bus. Ringing loop current detectors are shared by groups of the line circuits for detecting call answer signals during active ringing on a call and for controlling the line circuits to interrupt, or trip, the ringing upon a called party answer. Each group of the line circuits is permanently connected to a ringing current supply via an individual one of the loop current detectors. Each line circuit includes ringing control circuitry operated and released by the common control circuits for connecting ringing current to a called line during an active ringing interval and for disconnecting it during a silent interval of the ringing cycle.

Abstract: In telephone installations it is often necessary to know, without actually physically going off-hook, the status of the line. A solution to this problem is presented by the design of a low drain line status indicator circuit. Advantage is taken of the fact that the idle line voltage available from the switching machine is significantly greater than the busy line voltage. Accordingly, when the line is idle, a pulsating voltage is developed which is used to flash a light source at the station. When the line is busy or on hold, which situation can occur from a telephone station set connected to a remote extension, the line voltage is insufficient to enable the pulsating voltage circuit and, thus, the light source remains dark. In situations where one telephone station set serves two lines, the light sources associated with each line at each station location are arranged to flash in synchronism.