1. A signal that prepares a device to receive data or to perform a function.
2. In start-stop transmission, a signal at the beginning of a character that prepares the receiving device for the reception of the code elements.
Note: A start signal is limited to one signal element usually having the duration of a unit interval.

An on-hook signal indicating customer installation (CI) readiness to receive network outpulsing that is used in conjunction with controlled outpulsing. The on-hook signal that ends the wink-start signal or delay-dial signal is the start-dial signal. [T1.405-1989]

A transmission control character used as the first character of a message heading.

A transmission control character that precedes a text and may be used to terminate the message heading.

In facsimile systems, a signal used for starting the process of converting the electrical signal to an image on the record medium.

A character that includes one start signal at the beginning and one or two stop signals at the end.

In start-stop modulation, the ratio of (a) the maximum absolute difference between the actual and the theoretical intervals that separate any significant instant of modulation or demodulation from the significant instant of the start signal element immediately preceding it to (b) the unit interval.

In start-stop modulation, the maximum amount of overall start-stop distortion that is compatible with correct translation by the start-stop equipment of all the character signals that appear singly, that appear at the maximum allowable speed, or that appear at the standard modulation rate.

A method of modulation in which the time of occurrence of the bits within each character, or block of characters, relates to a fixed time frame, but the start of each character, or block of characters, is not related to this fixed time frame.

Synonym asynchronous communications system.