Timeline for How was parity used with modems?
Current License: CC BY-SA 3.0
11 events
| when toggle format | what | by | license | comment | |
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| Feb 20, 2017 at 10:26 | comment | added | Whit3rd | Some terminals (the venerable ASR-33) had internal parity generation and detection; it wasn't the modem (in the dumb-modem 110/300 baud days) that knew to check parity. | |
| Feb 16, 2017 at 13:35 | comment | added | RichF | Having been part of the crew of the USS Seawolf, SSN-575 for a number of years, I am aware of the concept. I was a reactor operator, though, not involved with the spy stuff. | |
| Feb 16, 2017 at 12:28 | comment | added | Chenmunka♦ | Incidentally, the modem links that I get involved with installing nowadays are typically cable runs in the tens of miles. | |
| Feb 16, 2017 at 12:22 | comment | added | Chenmunka♦ | @RichF: Don't forget that LAN systems use some form of Longitudinal Parity Checking too. The forms vary but the principle is the same. | |
| S Feb 16, 2017 at 12:14 | history | suggested | RichF | CC BY-SA 3.0 | clarification and usage of standard abbreviation (7E2) |
| Feb 16, 2017 at 12:11 | review | Suggested edits | |||
| S Feb 16, 2017 at 12:14 | |||||
| Feb 16, 2017 at 11:59 | comment | added | RichF | Ah, makes sense. More secure, both because of not being on the network and because the parity data streams are sensitive to any sort of violation. Cool. Is twisted-pair style wiring quiet enough to avoid passive invasion, or do such systems use fancier techniques to minimize data leakage along the wiring? | |
| Feb 16, 2017 at 10:52 | comment | added | Chenmunka♦ | @RichF: Whoops, well spotted - 7E2! Direct modem links - as opposed to LAN - are considered more secure as the only way to inject fake commands is to physically intercept the cable. Something that is easily detected. | |
| Feb 16, 2017 at 10:50 | history | edited | Chenmunka♦ | CC BY-SA 3.0 | Correction |
| Feb 16, 2017 at 10:40 | comment | added | RichF | Chenmunka, I am confused. Does not "7E1" mean 7-bit data, even parity, 1 stop bit? If so, what would 7E1 with 2 stop bits mean? Also, how does parity help improve security (as opposed to reliability)? (This sounds sort of negative. I don't mean it to be. I'm just curious.) | |
| Feb 16, 2017 at 8:39 | history | answered | Chenmunka♦ | CC BY-SA 3.0 |