IE870097L - Communication system - Google Patents

Abstract

Stock exchange work station desks, each with 12 loudspeakers, are connected by way of a TDM bus to respective selections of 12 lines out of 256 dedicated lines from which announcements may originate. To enable the connections of loudspeakers to lines to be more readily rearrangeable than is the case with a wired distribution frame, the 256 lines are multiplexed onto a bus 25 and each group of 12 desk loudspeakers has an associated desk card, such as 30, 31, which under control of a processor 33 selects 12 time slots corresponding to the lines required by the desk. A desk card such as 30 demultiplexes its selection of slots onto 12 separate analogue loudspeaker channels (Fig 6). A desk card such as 31 assembles its selection of slots into serial data form and transmits to the remote desk where demultiplexing to the loudspeaker analogue channels occurs (Figs 4 and 5). Each loudspeaker channel is voice switched, a threshold detector 34 putting a ninth bit into a line slot code to enable a loudspeaker channel if the level of activity is higher than a level set individually for each line by the processor 33, (Fig 7). If the level of activity falls below the threshold for more than 4 seconds the ninth bit is removed and any associated channel is disabled. <IMAGE> [DE3801055A1]