GB1361074A - Multiplexing apparatus - Google Patents

Abstract

1361074 Speech transmission systems ELECTRONIC COMMUNICATIONS Inc 17 Sept 1971 [30 Oct 1970] 43570/71 Heading G4H In a speech multiplexing system, preferably utilizing delta modulation, the sampling rate of the individual speech inputs is rendered dependent upon the number active at the start of a sampling interval. Speech inputs are each fed to a corresponding #-# A/D converter which is associated with a threshold logic device to provide an indication as to the activity of the related input, this indication being taken to set a flip-flop related to a corresponding stage of a ring counter comprising a series of flip-flops to remove the stage from the series if the source is inactive. The beginning of a sampling interval is defined by a clock pulse adapted to cause read in from the threshold devices and to set a "low" state into the first flip-flop of the series whose source is active. The counter is then clocked during the interval so that the "low" state is moved through all the stages with active inputs in a cyclic fashion to clock the relevant A/D converters in turn. Read-in from the threshold devices is effected, e.g. every 1 ms. The multiplexed data from the converters plus synchronizing and format data is transmitted using conventional apparatus to a receiver containing a clock synchronizer adapted to respond to call words in the transmission, and a distributer in addition to a similar ring counter providing outputs in a corresponding way as the first counter, to a plurality of D/A converters. Details of the multiplexing process are not described. Thus the sampling rate of any one source, whilst it is active, is altered at each 1 ms. interval. It is stated that this is sufficiently rapid to achieve an averaging effect in the human ear.