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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 no
by jamesdwilson 4y ago
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?
- klondike_ 4y agoPresumably uplink and downlink use different frequencies, similar to how duplex radio works
- psim1 4y agoNo need to presume; the ITU-T standards are surprisingly readable! https://www.itu.int/rec/T-REC-V.22-198811-I 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.
- deleted 4y ago[deleted]