Pelco C2622M User Manual

C2622M (2/07)

23

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Port is set to 
10BASE-T half-
duplex mode and no 
collisions are 
detected.*

—

If 10BASE-T half-duplex 
operation is desired, no action 
is required. If 10BASE-T half-
duplex operation is not 
desired, refer to Setting 
10BASE-T/100BASE-TX Port 
Modes of Operation on 
page 10 for information.

 *A collision is a normal event on a half-duplex Ethernet link. A collision occurs when two or more devices, 

referred to as stations, attempt to transmit at the same time on a shared physical medium.

Ethernet uses the CSMA/CD (Carrier Sense Multiple Access/Collision Detect) media access method by 
which two or more stations share a common transmission medium. Using CSMA/CD, a station monitors 
the medium and transmits a message in bit-serial form when it senses that no other station is 
transmitting. If, after initiating a transmission, the message collides with that of another station, each 
transmitting station then intentionally transmits for an additional predefined period to ensure 
propagation of the collision throughout the system. To avoid another collision, each station waits a 
random amount of time (backoff) before attempting to transmit again.

Excessive collisions occur when retransmission of a frame fails after 16 consecutive times and the 
frame is dropped. Excessive collisions may indicate that the network is becoming congested.

Table C.  Troubleshooting with Rear-Panel Indicators (Continued)