In 
telecommunications, a 
carrier sense multiple access with collision avoidance (
CSMA/CA) is a 
network control 
protocol in which (a) a 
carrier sensing scheme is used, (b) a 
data station that intends to transmit sends a 
jam signal, (c) after waiting a sufficient 
time for all stations to receive the jam signal, the data station transmits a 
frame, and (d) while transmitting, if the data station detects a jam signal from another station, it stops transmitting for a random time and then tries again.
Source: from Federal Standard 1037C
 
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