What do you call a line that connects a customer's site through a CO to a remote CO in another part of the country?

The line that connects a customer's site through a Central Office (CO) to a remote CO in another part of the country is commonly referred to as an FX line, or Foreign Exchange line. This type of line allows businesses or customers to establish a telephone number that is local to the area of the remote CO, thereby enabling them to connect to a distant location without incurring long-distance call charges.

FX lines are particularly useful for businesses that want to maintain a local presence in multiple regions without the need to physically operate there. This can enhance customer service and responsiveness for clients located in different geographical areas. Such functionality specifically distinguishes FX lines from other types of communications lines, as they focus on providing local access to remote exchanges.

The other options imply different uses or characteristics. A standard line generally refers to basic telephone lines without the special long-distance features of an FX line. Branch lines are typically associated with railway systems or less common telecommunication structures and might not accurately depict a dedicated line for customer connection across distances. An XDT line, in general terms, could imply various specialized functions, but it is not the recognized term for connecting customers to remote COs like an FX line is.