Ionica International Limited

Crosfield Electronics Limited

Gn Danavox A/s

Cognito Limited

Rupert Leslie Goodings

Leigh Carter

Neil Philip Piercy

Simon Alexander Black

Richard John Albrow

Paul Maxwell Martin

Peter F Ross

Ian W Rodgers

Roy Skovgaard Hansen

Philip H Wilson

Patrick Mitchell

Gideon A Senensieb

Transmission of digital data messages in digital telephony

Control signal transmission in digital radio telephony

The present invention relates to a method of transmitting digital data messages in predetermined time slots within fixed length time frames from at least one of a plurality of subscriber units to a base station for reception, in which, selectively, subscriber units which are members of one or more predetermined classes of subscriber units are restricted from transmitting at least one predetermined type of message. This advantageously helps in avoiding overload of the network. The invention also relates to corresponding communication means.

Method for restricting channel access depending on subscriber classes

Transmission of control messages in digital telephony

Transmission timing control in digital radio telephony

Radio data communication system having means for reducing collisions

A hearing aid includes a filter in an electrical feedback path, the characteristics of which filter are calculated to model acoustic coupling between the receiver and microphone of the aid. A limiter is inserted in the main electrical pathway between the microphone and the receiver to provide stability in the presence of sudden sound bursts. A noise signal is injected continuously into the electrical circuit and is used to adapt the characteristics of the filter to accommodate changes in the acoustic coupling. The level of the noise signal can be varied to match changes in residual signal level to maintain signal to noise ratio and to optimize rate of adaption commensurate with satisfactory hearing function while the noise itself is unobtrusive to the user.

Hearing aid having compensation for acoustic feedback

A method and apparatus for decoding a digital codeword of a codeword system comprising digital codewords of varying length in which no short codeword forms the prefix of a longer codeword in the same system comprises detecting with means (26) whether the codeword has a predetermined prefix, the predetermined prefix being shorter than any codeword containing it. Further means (26) are provided for decoding only the suffix of the codeword or the entire codeword respectively according to whether or not the predetermined prefix is detected.

Codeword decoding

A method and apparatus for coding signals representing a stream of digital data groups (for example run lengths) for transmission or storage, each group representing a numerical quantity, is described. The signals are supplied via input and modify registers (4,6) and an encode latch (11) to a set of encode PROMs (12). The PROMs (12) generate for each data group a code representing the group, the code comprising a terminator codeword and, where necessary, one or more make-up codewords. The codewords are based on one or more multiplicative modifiers. The codewords are fed in parallel to output registers (13,14) and then serially shifted out of the output registers for subsequent transmission, storage, or further processing.

Data coding

A method and apparatus for detecting digital codewords or predetermined portions of digital codewords in a stream of codewords is described. The apparatus comprises a shift register (21) having a length at least one bit greater than the length of the longest codeword or predetermined codeword portion to be detected; and means including an inverter (24) for loading the shift register (21) with the logical complement of the leading bit of the stream of codewords. A clock (25) is provided to cause data in the data stream to be serially shifted into the shift register (21). The contents of the shift register after each shift are then used to address one or more PROMs (26) to determine whether the data in the shift register (21) upstream of the first change between data in the shift register of one type and data in the shift register of the complementary type comprises a codeword or a predetermined codeword portion.

Detecting codewords

Growing community of inventors

Cambridge, United Kingdom

Rupert Leslie Goodings