UNIT FOR ADAPTING THE AUTOMATIC SWITCHING MEANS DESIGNED FOR ANALOGUE RADIO LINKS FOR DIGITAL DATA SIGNALS

摘要

1528380 Radio communication systems CSELTCENTRO STUDI E LABORATORI TELECOMUNICAZIONI SpA 24 Nov 1975 [25 Nov 1974] 48155/75 Heading H4L A conventional analogue radio signal transmission system which includes an automatic switching means requiring for its operation a pilot signal having a frequency f p and a noise signal centred about a frequency f r is adapted for digital data signals, which are not accompanied by a pilot signal f p and which have a noise signal centred on a frequency f 1 rather than f r , by the provision of a unit SPR which provides the required signal f p and which converts the received noise signal at frequency f 1 into a noise signal at the required frequency # r . As shown, a digital signal including noise in a frequency band centred on a first frequency f 1 is received at terminal 1 for processing so that a switching network CCA can be provided with a pilot signal and with a signal at a second frequency f r , the latter signals being necessary for the correct functioning of the network. Thus, the received signal is fed to a filter PA passing only frequencies centred on f 1 , the output from the filter being applied to a frequency converter TF associated with an oscillator AA such that the output from TF, filtered at PB, is at the required frequency f r . An oscillator AB generates the pilot signal which is passed, and a switch C controlled by a synchronization recovery circuit RS, to an adder which also receives the output from filter PB, the adder output being supplied to the network CCA. The adder may be omitted, the required signals then being separately supplied to the network.