Racal Data Communications Inc.

Racal-datacom, Inc.

Other

Racal-milgo Limited

Milgo Electronic Corporation

Ming-Luh Kao

Jerry A Miller

Jong-Keung Cheng

Mario De La Guardia

Jay P Jayapalan

Charles R Baugh

Jack E Stephenson

Angela W Kao

George Raymond Kushin

Lih-Ju Chern

A dialed telephone connection can be implemented as an end-to-end digital connection by virtue of switched voice transmission facilities becoming more prevalent. If such a connection is detected, it is possible to transmit digital data over the connection at a much higher rate than using analog technology. A dialed voice call is emulated to set up such a connection and the connection is then tested to determine if it is end-to-end digital. If so, high speed digital data can be passed. If not, the connection is broken and then reestablished repeatedly until such a digital connection is found. In one embodiment, the calls are alternately initiated from each of the two parties involved in attempts to increase the likelihood of achieving an end-to-end digital connection. If no such connection can be obtained after a reasonable number of tries, an analog communication session can be established.

High speed digital data transmission over switched voice network

A combined data compression/error correction system suitable for use in synchronous communication utilizes a data compressor to produce variable rate compressed data from synchronous data. The variable rate compressed data is applied to a FIFO memory which is monitored to determine when the amount of data in the FIFO drops below a predetermined threshold. When it drops below this threshold, an error correction code generator generates a separator character and an error correction code which is appended to the compressed data in the FIFO. Thus, the additional bandwidth created by data compression is used to provide enhancement to the data integrity by providing a variable level of error correction varying in accordance with the free bandwidth generated by the data compressor.

Data compression with error correction

A device for providing teleconference capabilities in an ISDN includes a first receiver for receiving a first signal representing a first message over a first ISDN B-channel. A second receiver receives a second signal representing a second message over a second ISDN B-channel. A receive mixer mixes the first signal with the second signal to produce a receive mixed signal. A local receiver receives a local signal representing a local message to be transmitted over the first and second ISDN B-channel. A first transmit mixer mixes the first signal with the local signal to produce a first transmit mixed signal. A first transmitter transmits the first transmit mixed signal over the second ISDN B-channel. A second transmit mixer mixes the second signal with the local signal to produce a second transmit mixed signal. A second transmitter transmits the second transmit mixed signal over the first ISDN B-channel.

ISDN terminal adapter with teleconference provision

A data modem includes a data compression circuit which compresses incoming data prior to transmission. The compression ratio obtained from the compression process is used to select a constellation for transmission of the data. When higher compression rates are achieved, fewer constellation points (symbols) representing fewer bits per point are transmitted. In this manner, incoming data rate can be held constant while utilizing a more robust constellation which has greater immunity to transmission line impairments. This reduces errors and retransmissions which can ultimately lead to reduction in effective throughput in conventional systems.

Modem with data compression selected constellation

In a method for compensating for differences in a first clock signal's rate and a second clock signal's rate, transmitting voice samples from a first location synchronized to the first clock signal are received at a second location having a second clock for generating the second clock signal. The first clock signal and the second clock signal are compared to determine when a slip of one cycle has occured and it is determined which of the first and second clock rates is greatest. At the second location, the process includes adding a received voice sample for each predetermined number of slips which occur if the second clock is running too fast relative to the first clock, and discard an additional voice sample for each predetermined number of slips which occur if the second clock is running too slow relative to the first clock.

Sampling clock synchronization

An apparatus for providing remote answering of a doorbell includes a circuit for receiving a doorbell signal indicative that a doorbell switch has been actuated. An autodialing circuit is coupled to and responsive to the receiving circuit and a telephone line for dialing a telephone number responsive to the doorbell signal. An alerting circuit generates an alert signal to be transmitted over the telephone line to the telephone number dialed by the autodialing circuit, so that the alert signal may alert a party answering the remote telephone to the fact that the party is responding to a doorbell rather than a normal telephone call. An audio speaker is physically situated near the doorbell switch, for reproducing audio signals from the telephone line which are generated at the remote telephone. An audio microphone is also physically situated near the doorbell switch, for generating electrical signals responsive to sounds made near the doorbell switch and transmitting the signals to the telephone line to the remote telephone. The apparatus further includes a switching network for coupling the door speaker and microphone to a local telephone set and a remote telephone set selectively in any combination.

Method and apparatus for remote doorbell answering

A method of providing B channel diagnostics to an integrated services digital network (ISDN) comprises the steps of monitoring error performance on the ISDN D channel and comparing the D channel error performance to a predetermined criterion as a measure of the B channel error performance. If the predetermined threshold is exceeded any of a number of possible actions can be taken by a network diagnostics controller including various loopback tests, alerts or network reconfiguration.

Access circuit diagnostics for integrated services digital network

A microprocessor-based system is provided with a non-volatile store (such as a PROM) which stores a bootstrap program, a non-volatile store (such as an EPROM) which stores one or more program overlays, and a programmable volatile store (such as a RAM) which can be written into and read from. When the system is powered up, the microprocessor executes the bootstrap program out of the PROM. The bootstrap program includes instructions which copy the program instructions stored in the EPROM into the RAM. The microprocessor then executes the program instructions out of the RAM. Program instructions may be stored in the EPROM in a plurality of overlays, and individual overlays selected by either the bootstrap program or instructions contained in another overlay may be selectively loaded into the RAM for execution. The EPROM is addressed by a programmable counter which appears to the microprocessor as an input/output device to be written into.

High speed program store with bootstrap

An all digital video synchronization technique wherein a microprocessor tracks the incoming video signal and synchronizes its operation by stopping at a certain point in the sync signal and restarting upon occurrence of a horizontal sync pulse.

Digital video sync detection

A microprocessor-based video sync generation technique wherein the microprocessor stores a table of transition times and at each time supplies appropriate control signals to a digital-to-analog converter to cause it to generate the desired sync waveform.

Processor controlled digital video sync generation

A thermometer or bouncing-ball LED display system provides a fast response, easily readable, quantitative indication of a variable. A received analog signal, representing the variable to be displayed, is effectively compared with an analog signal representing the present display indication. The difference therebetween is averaged over a sampling period. If this average difference exceeds a predetermined limit in either a positive or negative direction, the display indication is changed to reflect this difference. The sensitivity of the display can be selectively determined by increasing or decreasing the sampling frequency and the predetermined limit. The display system can be selectively operated in three different response modes. In a fast-attack, slow-release mode, the display indication is changed more rapidly in response to positive direction differences in the compare stage, than in response to negative direction differences. In a fast mode, the display indication is changed rapidly in response to either positive or negative direction differences in the compare stage. In a slow mode, the display indication is changed less rapidly in response to either positive or negative differences in the compare stage.

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Miami, FL, United States of America

Ming-Luh Kao