4 ms·

I am not sure where you're going with that, but the statement about needing a digital hookup isn't correct. A 56k analogue modem running over POTS offered 56kbp

I am not sure where you're going with that, but the statement about needing a digital hookup isn't correct. A 56k analogue modem running over POTS offered 56kbps in one direction, and between 1200/2400/9600bps in the opposite direction.

icedchai 5y ago
He is correct in that the ISP side needed to be digital. Typically it was done using a PRI line, which was basically a ISDN T1: 23 "lines" (B channels) plus 1 signaling channel (D channel.) The ISPs I am familiar with used "Ascend Max" equipment.
- justinlloyd 5y ago
  My memory is somewhat hazy on that. I do recall helping to hook up equipment (cannot recall the brand) to the T1 DSU/CSU for our multiline "adult" ISP, but that wasn't my area of responsibility at the time. And I am going to take back my "56k in one direction" statement and say: I think we capped out at around 33k on the analogue to analogue connections even though they "supported" 56k so I am probably quoting our crappy marketing rather than our physical capability.
  - icedchai 5y ago
    My understanding is there was no way to support full 56k between two analog modems, so one side needed to be digital. In reality, I never saw a 56k connection even in that configuration. It was always ~52k or lower, but maybe we just had crappy phone lines around here.
    - justinlloyd 5y ago
      I am recalling getting "insane" speeds during site-to-site warez transfers on the BBS's, upwards of 200kbps a second, capping the CPU on most machines, but we also used shotgunned modems on the main trading hubs, and a packetizing ZModem-like protocol to separate the transfers into 64Kbyte chunks so I am most likely misremembering a number of misadventures and smushing a few of the details together.
      - icedchai 5y ago
        That seems possible with compression? Most serial ports maxed out at 115,200 bps back in those days.
nikanj 5y ago
56k was achieved by removing one analog-digital conversion. Instead of your my computer (digital)-my modem (analog)-phone network (digital)-your modem (analog)-your computer (digital), it was my modem (analog)-phone network (digital)-digital trunk-your computer. A 56k modem at a bbs would just work at 33.6k

icedchai 5y ago

He is correct in that the ISP side needed to be digital. Typically it was done using a PRI line, which was basically a ISDN T1: 23 "lines" (B channels) plus 1 signaling channel (D channel.) The ISPs I am familiar with used "Ascend Max" equipment.

justinlloyd 5y ago
My memory is somewhat hazy on that. I do recall helping to hook up equipment (cannot recall the brand) to the T1 DSU/CSU for our multiline "adult" ISP, but that wasn't my area of responsibility at the time. And I am going to take back my "56k in one direction" statement and say: I think we capped out at around 33k on the analogue to analogue connections even though they "supported" 56k so I am probably quoting our crappy marketing rather than our physical capability.
- icedchai 5y ago
  My understanding is there was no way to support full 56k between two analog modems, so one side needed to be digital. In reality, I never saw a 56k connection even in that configuration. It was always ~52k or lower, but maybe we just had crappy phone lines around here.
  - justinlloyd 5y ago
    I am recalling getting "insane" speeds during site-to-site warez transfers on the BBS's, upwards of 200kbps a second, capping the CPU on most machines, but we also used shotgunned modems on the main trading hubs, and a packetizing ZModem-like protocol to separate the transfers into 64Kbyte chunks so I am most likely misremembering a number of misadventures and smushing a few of the details together.
    - icedchai 5y ago
      That seems possible with compression? Most serial ports maxed out at 115,200 bps back in those days.

nikanj 5y ago

56k was achieved by removing one analog-digital conversion. Instead of your my computer (digital)-my modem (analog)-phone network (digital)-your modem (analog)-your computer (digital), it was my modem (analog)-phone network (digital)-digital trunk-your computer. A 56k modem at a bbs would just work at 33.6k