Abstract: A local communication system has a number of stations (10,12,13,14) connected for the communication of messages by one or more data channels (16). One of the stations (14) comprises a display device operable to display messages sent by other stations (10,12) in separate ones of a plurality of fields. A station (10,12) sending a display command and message to the user output subdevice (41) of the display device includes field separators identifying discrete parts of the message to be displayed in successive fields of the display and the message portions may be sent as separate messages.

Abstract: A local communication system has a number of stations connected for the communication of messages by one or more data channels. One of the stations comprises a display device operable to display messages sent by other stations in one or more of a plurality of fields. Each message to be displayed is given a display lifetime (80-84), which is determined by a mode value (74-78) set by the originating subdevice or commonly assigned by the display device. The display determines whether there are sufficient display fields available (68) to display a received message and handles the timing (88) and subsequent removal from display (90) of a message on expiry of its display lifetime, independently of the originating station.

Abstract: The test apparatus (PC,KB,DIS,PR,IF) communicates via a standard serial bus (12) with a device under test (DUT) to verify conformity with a standard application protocol defining the format, meaning and applicability of messages passed via the bus (12). The apparatus generates a test sequence of commands and requests and analyses the replies of the DUT for conformity. The test sequence and the analysis are adapted automatically in response to previous replies of the device, to provide a thorough but efficient test of the device and any subdevices identified within it. Where the standard application protocol defines extended autonomous cooperation between devices, the test apparatus emulates one or more further devices to be controlled and interrogated by the device under test.

Abstract: A local communication system has a number of stations (10,12,13,14) connected for the communication of messages by one or more data channels (16). One of the stations (14) comprises a display device operable to display messages sent by other stations (10,12) in separate ones of a plurality of fields. A station (10,12) sending a display command and message to the user output subdevice (41) of the display device includes field separators identifying discrete parts of the message to be displayed in successive fields of the display and the message portions may be sent as separate messages.

Abstract: In a single channel communication bus system, e.g. D.sub.2 B, sometimes two devices of the same type must be initialized at the same time. These devices start out with the same address installed by the manufacturer. The installed address includes follower bits which can be changed to account for the presence of other devices. During initialization, all devices are set to a dummy address and the installed address is stored. Each station then looks for devices having its own installed address. If, after 3 tries, none is found then the stored address is used. If other devices having the installed address are found, the follower bits can be changed. The station iterates until all possible follower bits are exhausted. In this way the stations of the same type have an improved likelihood of being initialized with distinct addresses.

Abstract: Apparatuses (1,2,3) of an audio/video system convey user commands to one another via a serial control bus (4). The user commands convey key activations on a remote handset (18a), whose keys include both "normal" keys such as "mute/unmute", and "repeat" keys such as "volume up" and "volume down". To convey a repeat key activation, a first control means (12) within one apparatus addresses a key activation message to a second control means (32) within another apparatus. The second control means (32) synthesises locally a repetitive series of user commands, until a key release message is received. The need for repetitive user command messages to be sent via the control bus is thereby eliminated, and the frequency of repetition can be defined locally to give consistent response to user commands. The second control means (32) can also implement a de-bouncing function, disregarding duplicate user command messages sent by a third apparatus (2) which also responds to the handset (18a).

Abstract: A local communication system has a number of stations connected for the communication of messages by one or more data channels. One of the stations comprises a display device operable to display messages (M1, M2) sent by other stations in one or more of a plurality of fields (F1, F2, F3). On receipt of a display command and message the user output subdevice of the display ascertains whether there are sufficient display fields available to display the entire message and, if so, allocates display fields to the message. Messages from two or more stations may be displayed simultaneously if there are sufficient available fields, with the user output subdevice allocating an appropriate number of fields to each message.

Abstract: A multistation single-channel communication bus system accommodating master stations and slave stations, with any master performing arbitration, arbitration outcome detection, and, upon winning the arbitration, formatting a frame having a slave address and slave control signals, and accommodating data byte periods for data transmission from a transmitter station to a receiver station up to a first maximum data byte length. Each period accommodating an acknowledge bit from the receiver station. The transmitter station responding to the absence of the acknowledge bit for a particular data byte by repeating that data byte. The system, for a message whose data byte length would exceed the first maximum, divides the message into partial messages each of an associated frame data byte count below the first maximum, and assigns each partial message to a respective bus frame. The system counts, in a particular frame, data byte periods and received acknowledge bits.

Abstract: A number of domestic audio/video apparatuses (10,12,14) are interconnected by a Domestic Digital Bus (16) for the exchange of control information. A User I/O subdevice (41) in one apparatus is addressable by a control subdevice (22) of another apparatus to allow the display of menu items defined by the control subdevice. The User I/O subdevice returns user control signals by reference to the defined menu items. The right of menu control can be transferred via the User I/O subdevice to and from other control subdevices (20 etc.) to allow integration of the menu control functions of the different apparatuses.

Abstract: A system of domestic audio-visual apparatuses (10-18) are connected on a one-to-one basis (20-26) for the exchange of video and audio signals. The apparatuses are also connected to a serial data bus (28,D2B) which allows distributed control messages to be sent and received by the apparatuses (addressable as `devices`) and elements of the apparatuses (subdevices). No apparatus has knowledge of the complete system of connections (20-26). An autonomous process (100, 102, 104, 110') can be initiated whereby a signal path from a source subdevice (64) to a destination subdevice (62) is identified step by step using the local knowledge of each apparatus. The speed of this process can be improved by initiating (101) a concurrent second autonomous process (106') whereby a signal path is identified from a third subdevice (42) to the destination subdevice.

Abstract: A system of domestic video apparatuses (10,12,14 etc.) are interconnected by video cables (64,66,68) and also by a serial data bus (D2B,16) having distributed control intelligence (20,22). Within each apparatus, signal generator and/or detector functions are defined, which can be activated and controlled via the bus (16). The video cable connections (64,66,68) between various plugs (26-1,2,3, 52-1,2,3, etc.) of the apparatuses (10,12,14) are identified automatically by interrupting signal transmission from all apparatuses involved then allowing a single transmission from an input to the connections and detecting the where the signal is output. By repeating the process with other all connections may be traced. The automatic identification of cable connections occurs without requiring additional conductors for cable detection signals.

Abstract: The system comprises a number of stations interconnected for the communication of control messages which are multiplexed with digital audio signals. The control channel is divided into eight parallel channels, and each station is allocated one channel to transmit on, while it receives from other stations on the other seven channels. Messages on each channel are segmented into finite message units. When a longer message is to be transmitted, the receiving station implement a locking mechanism such that message units will not be accepted on other channels until all message units of the message have been received. To allow the number of stations to exceed the number of data channels, some of the stations are designated "slave only", and share a single channel for the transmission of control messages. To avoid conflicts, these stations are permitted to transmit only in response to request messages from a station having its own exclusive transmit channel.

Abstract: Apparatuses of an audio/video system convey user commands to one another via a serial control bus. The user commands convey key activations on a remote handset, whose keys include both "normal" keys such as "mute/unmute", and "repeat" keys such as "volume up" and "volume down". To convey a repeat key activation, a first control means within one apparatus addresses a key activation message to a second control means within another apparatus. The second control means synthesises locally a repetitive series of user commands, until a key release message is received. The need for repetitive user command messages to be sent via the control bus is thereby eliminated, and the frequency of repetition can be defined locally to give consistent response to user commands. The second control means can also implement a de-bouncing function, disregarding duplicate user command messages sent by a third apparatus which also responds to the handset.

Abstract: A multistation communication bus system including a plurality of master stations and a slave station for transmitting information from the master stations and slave station using a frame based arbitration process. The master station which wins the arbitration transmits a framewise organized message including locking and unlocking signals for respectively, locking and unlocking an addressed slave station, thus blocking any other master station from accessing the slave station for a duration of multiple frames of the message.Any other master station, upon detecting this blocking condition, executes a first sequence of retry undertakings at a combined time length that is substantially less than a standard maximum value of the duration. A second sequence of less frequent retry undertakings at a combined time length that is more than a standard maximum value of the duration may then be attempted.

Abstract: A domestic video system includes a number of interconnected video apparatuses (10,12,14), at least one of the apparatuses including a facility for conversion of the aspect ratio of video signals. The system further includes control signalling (20) operating via a standard serial bus (16) for systematically interrogating each apparatus in a signal path to determine whether aspect ratio conversion is necessary in the signal path and for selectively enabling or disabling any conversion facility in the signal path to effect such necessary conversion. The control means implements a strategy for eliminating unnecessary conversion of aspect ratio in the signal path, and also chooses to effect conversion as late as possible in the signal path when faced with more than one available conversion facility.