This component may be called a station valve, a station ‘T’ or a vacuum sequencing valve. In all cases, it is an air-actuated valve that controls the flow of vacuum at each station receiver. A station valve is required for every receiver in a central system. They are usually made of aluminum and their inlet/outlet tubes are sized to match the diameter of the vacuum line.
Station valves are attached to the vacuum line associated with each receiver. They can be mounted over top or even behind the receivers. They often include a pop-up indicator, which is a visual indication of whether the station is working properly or not.
They may also be built into or on top of each receiver. The built-in station valves make receiver installation easier but they do add to the bulk and weight of the receivers.