Understanding CSMA/CD

Question

Computer networks

Good afternoon, a couple of questions.
1. How does the source understand that a collision has occurred?
2. What does it mean to listen to the transmission medium?
Both questions mean exactly how.

Answer 1

1. As far as I remember, when an accident occurs (between data), a broken signal is sent. When the nodes receive it, they send a Jam signal for other nodes to detect the collision.
2. When the node's network adapter receives data not addressed to it, it deletes them, but if the sniffer is running, we can capture this data.

Answer 2

The source has something like a voltmeter, when a collision occurs, this voltmeter will notice an increase in voltage above normal.
2nick5: When the sniffer is running, the interface is switched to the so-called "promiscus" mode - it does not look at the mac address and transfers all packets to the operating system.

Answer 3

Hmm. It's simple, one card transmits (on one pair of wires), at the same time it listens to what is on the second pair (which is for reception), if someone starts transmitting at that moment, the card will hear, stop transmitting, send JAM (in case CSMA/CD) and will wait for a random time. Actually, everything is perfectly described in the Wikipedia article:
“Carrier Sense” describes the fact that a transmitter uses feedback from a receiver that detects a carrier wave before trying to send. That is, it tries to detect the presence of an encoded signal from another station before attempting to transmit. If a carrier is sensed, the station waits for the transmission in progress to finish before initiating its own transmission.