On 07/01/14 05:53, Tom Minnis wrote:
I believe the Western Electric D1 channel bank was the first and the European standard came along later. Then came the D2, the D3 and finally the D4 when integrated codecs finally came to be and it was practical to get rid of the common codec and do it channel by channel. I have tried to look at the spectrum of AM broadcast radio when they are taking phone calls and you can defiantly see the low frequency roll off starting around 300Hz for the guy on the phone and when the guy at the station talks, there are strong components below 100Hz.
First came the TDM replacements of FDM trunks, first system I know of is from 1953 and predates the Western Electric D1 channel bank by 9 years. It was only when TDM switching was introduced that things started coordination and standardisation, as the TDM trunks could be incompatible as the interconnect was done in analog signals.
Cheers, Magnus _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
