As an alternative, R or L can be specified. 1N, 1A, 2N, 2A are allowed values for MkIV telescopes. In addition, the racks can be switched so that they provide one bit samples from all 14 BBCs or 2 bit samples from the first 8. The mapping is now different than it used to be. The VLA computer selects which antenna or sum port to use depending on the mode and on the reference antenna given by the operators.
Nothing is required in the schedule files to specify the mapping explicitly.
The switch is very general so other mappings are possible, but the above will be the normal setup. An array of up to 16 characters of length 2. Defaults to previous station.