In the context of FastEthernet, which device commonly uses pins 1 and 2 for transmission?

In FastEthernet, pins 1 and 2 on an RJ45 connector are used for transmitting data when operating in a 10BASE-T or 100BASE-TX network. This pin configuration is standard for the transmission of data in the IEEE 802.3 Ethernet specification.

Routers are devices that frequently utilize these transmission pins, as they handle the routing of data packets between different networks. When a router receives data from a connected device, it uses these pins to transmit that data to the appropriate destination or to forward it to another network.

The roles of other devices such as switches, firewalls, and PCs in Ethernet networks do involve using these pins for transmission as well, but the question focuses on the context of the common use and the operational capacity of routers specifically in a network environment. Thus, while devices like switches and PCs do also have roles in data transmission, the emphasis on routers aligns with their primary function in network management and data routing.