28 Jun '16, 2pm

Serially, Are You Syncing or Asyncing?

“The telegraph system considers an idle line to be high. With the signal line held high operators could detect physical breaks in the line because the signal dropped to zero. To send a message a telegraph operator moved a slide on the key to “break” the line. The slider was put back when the message was completed.” Though Teletype was descended from telegraph, they work slightly differently. They are both current loop systems. Think of the telegraph keys as switches, connected in series (you can have more than two telegraph stations on a circuit). For one key to be able to make and break the loop, all the other keys need to be in the “shorted” position. But a telegraph system uses an open loop as a normal state, closing the key completes the loop and causes current to flow through the sounder magnets (connected in series with the keys in the loop). So between characters se...

Full article: http://hackaday.com/2016/06/28/serially-are-you-syncing-o...

Tweets