Next, consider a more modern photometer that uses pulse-counting. It has a ``neutral'' filter in addition to standard uvby filters. The ``neutral'' filter is in series with the passband filters, and is used to determine the dead-time correction. The positions of these two filter mechanisms are recorded as two adjacent digits in the data, so we can treat them as a single filter code; the second digit is 1 when the ``neutral'' filter is in the beam.
There is also a shutter whose position is encoded separately in the data stream: 0 means open, 1 means shut. This can be treated as a second logical filter mechanism.
The photomultiplier in this modern instrument is in a thermoelectrically cooled
chamber, regulated to run at 
C (273 K).
Table 
shows what we get.
Again, there is only one detector, so we need not include the NDETUSED column.
Table: Instrument table file for a two-channel photometer