There are multiple categories of indoor phone cable. In the past, Category 3 was the most advanced with a possible bandwidth of 16 MHZ. Today, many applications require a cable with a higher bandwidth so many opt for Category 5, 5 enhanced or 6. That is where Cat 5, 5e and 6 come in to play. They run at 100 MHZ or higher making the transfer of voice and data faster and more reliable. However, it is worth noting that these higher rated categories rarely are manufactured in higher pair counts (over 50) and they do not allow longer cable distances for Ethernet networks.