Re:The sound of the dialup, pictured (2012)
by jamesdwilson on Friday January 13, 2023 @02:33PM
(#34372742)
One thing I never quite understood about dialup is how they managed to handle duplex communication. That is, when one side is talking, how did the other side not talk over it, or how did they take turns, or how did they discern who said what.. like when one side was broadcasting, didn't it muddle up the audio on the other side?
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Re:The sound of the dialup, pictured (2012)
by klondike_ on Friday January 13, 2023 @02:44PM
(#34372883)
Presumably uplink and downlink use different frequencies, similar to how duplex radio works
Re:The sound of the dialup, pictured (2012)
by psim1 on Friday January 13, 2023 @05:14PM
(#34374643)
No need to presume; the ITU-T standards are surprisingly readable!
https://www.itu.int/rec/T-REC-V.22-198811-I
For this older standard (1200 bps using FSK modulation) it does indeed use separate bands (from section 6.1):
On the general switched telephone network, the modem at the calling data station shall transmit in the low channel and receive in the high channel (call mode). The modem at the answering data station shall receive in the low channel and transmit in the high channel (answer mode).
The newer modem standards are far more sophisticated and I don't know anything about them. I picked this one because I had been working with V.22 in the past year.