AT&T 610 - On-Line Signaling

User's Guide
August 1985
On-Line Signaling
Co_unications
Page 9- 7
In asynchronous signaling, start and stop bits are required
in the bit stream to identify the beginning and ending of a
character. The start bit is a positive going transition (space)
on a marking line. It signals that the following voltage
transition will be an ASCII character. Each group of character
bits is followed by a stop bit. The stop bit is a negative
going transition (mark) of what would be the 9th information
bit. This signaling pattern is commonly referred to as "10 bit
code" or "10 unit code."
(Perfect waveform for ASCII character M with even parity
shown. )
State
{IJ _ .... 1 Start W 2
5
3
4
State 1 (mark)/Off = -5 to -25 Vdc
State 0 (space)/On = +5 to +25 Vdc
6
..... 7 ... 1 pa~ty I Stop
Figure 9-9. On-Line Signaling