When is site-to-site transport perfected in Star Trek?

Question

In the Star Trek: Discovery Episode S01E05 Choose Your Pain we see Saru order that Captain Lorca be transported back from the Klingon vessel.

In Star Trek: Enterprise transporter technology is still being perfected.

We know that transporters can either be:

1. From the transporter room
2. To the transporter room
3. From one transporter room to another transporter room
4. Where no transporter room is the source or the destination: site-to-site transport.

It's not clear when site-to-site transport was first perfected.

The following commentator writes (about this episode):

Site to site transport in a prequel?

My question is: When is site to site transport perfected in Star Trek?

Answer 1

The first use, chronologically in real life, of what could be considered a Site-To-Site transport in Star Trek would be in The Original Series episode A Piece of the Action, in 1968, "Montgomery Scott transported Tepo directly from his headquarters to those of Bela Okmyx." The first use of the words "site-to-site transport" would be in The Next Generation episode Brothers, 1990, when "Miles O'Brien disabled the site-to-site transport function to stop Data from beaming off the bridge in 2367. The android was able to reactivate it."

Given this, it seems likely that site-to-site transport has been available at least as far back as TOS. It's not something that was invented in Voyager (although they used it quite a lot more there), so it's not all that bad that it's used in a prequel.

Answer 2

There is not much difference between all the forms of transport that you list: all of them require a transporter room and its equipment, most notably a transporter pattern buffer, a device that stores all information about the dematerialized matter before streaming it to its destination.

In example, transporting from a transporter room to an external site required dematerializing the matter present on the transporter platforms, storing the matter stream into the pattern buffer, then transporting it to the destination site; transporting to a transporter room, was effectively the opposite process.

Site-to-site transport, was not that different: it dematerialized the subject from its location (outside the transporter platform), streamed the matter information to the pattern buffer, then streamed again all this information to the destination site.

According to the TNG Technical Manual:

Site-to-site transport. This refers to a double-beaming procedure in which a subject is dematerialized at a remote site and routed to a transporter chamber. Instead of being materialized in the normal beam-up process, however, the matter stream is then shunted to a second pattern buffer and then to a second emitter array, which directs the subject to the final destination. Such direct transport consumes nearly twice the energy of normal transport and is not generally employed except during emergency situations. Site-to-site transport is not employed during emergency situations that require the transport of large numbers of individuals because this procedure effectively halves the total system capacity due to minimum duty cycle requirements.

So, basically, a site-to-site transport is a sequence of a beam-up immediately followed by a beam-down, where the object is not re-materialized and re-dematerialized in between. It is not always used because it requires a greater amount of resources.

You can thank about it like your laptop (= a Transporter room) with two USB pendrives attached (= site A and site B): if you want to move files between one of the to the other, you don't need to physically copy them to your hard-drive (= materialize and dematerialize again), but you can directly copy them (= site-to-site transport) even if you still need the processing power and the RAM of your laptop (= trasporter equipment and pattern buffer).