Passive repeaters were certainly not common, possibly not used at all in the AT&T Long Lines network. I am not aware of any examples at least. In general AT&T d

Passive repeaters were certainly not common, possibly not used at all in the AT&T Long Lines network. I am not aware of any examples at least. In general AT&T did not like them, it's more common for telephone passive repeaters to have been installed by CLECs or telephone cooperatives, and later on I know MCI used some in this area. These were all later installations than most Long Lines. I'm not sure exactly why AT&T eschewed them besides the speculation that AT&T built much of their microwave network relatively early and so the attenuation may not have been acceptable given the already short range on their links. AT&T's first generation of microwave sites had to put the RF amplifier in a hut on top of the tower because the waveguide loss was unacceptable, for example. A very common place to find passive repeaters in the desert west is at dams, where they were almost invariably installed to provide the telephone connections to the power house. A later interesting example of passive reflectors is the "periscope antenna," mostly used by Western Union when they operated a microwave network for a time. The actual microwave antennas were mounted on the roof of the shack pointed up, and at the top of the tower passive reflectors at a 45 degree angle "bent" it to horizontal. It put the more maintenance intensive parts on the ground at the cost of some power loss.