Back in the late 60's and early 70's i install hundreds of these. That outlet is made by Blonder-Tongue. Jerrold also made them. They were tap style. Each had a tap rating in db as to how much signal they passed from the trunk cable. They made them in 300 Ohm screw terminals or 75 Ohm F or G jack. You would put 8 or so on a run using lower loss taps to the end. This would compensate for the cable loss. Most were rated for VHF signals only, any UHF stations were converted to VHF at the Head End. Channels were received by an antenna, UHF converted to VHF, amplified, and distributed thru splitters and then to drops to which these outlets were installed. Mostly used in apt & multi-unit housing.
