Looking for a short novel (perhaps from a collection) from sixties or seventy’s. A method of teleportation has been developed whereby people can explore planets by creating a replica of themselves on the target planet. Apparently there are few humans and more and more they spend their time with these teleportation machines. The story opens with the discovery of a new planet with an apparently abandoned city. A team (perhaps only two) begin to explore the city and find that things in the city still work, particularly a transportation system. I can’t remember too many of the details of the exploration of the city but ultimately they come upon a place where the ‘residents’ of the city are. They are totally immobile and are being kept alive artificially. Somehow they kill one of the ‘residents’. They are arrested by robots(?) who are the caretakers of the city. The robots put them on trial and they are convicted and condemned to death. Just before the execution the humans ‘disconnect’ and are no longer there. One of the humans then returns to the planet and lectures the robots on the moral implications of keeping the residents alive as they are and the path the robots took to bring them to that existence. The novel ends with the human disconnecting, then getting up from his teleportation machine realizing that humans are becoming too dependent on machines and the fate that may befall them. Any ideas?