There are four cold mirrors in KAGRA, two at the center and one each at the end of the 3km tunnels.
Each cold mirror is installed in a cryostat. Each cryostat has 4 cryocoolers. Each cryocooler is powered by a compressor.
We use the diagnostic interface connector. The pin-out is listed in Table 1 of p54 (p50 at the bottom of the page).
We will use pin #10 and #14 to #20.
There will be four compressors per cryostat. Therefore, the total number of compressors is 16.
We will have 64 temperature sensors per cryostat. There are 4 cryostats. Therefore the total number of the temperature sensors is 256. Each temperature sensor has a differential voltage output. The voltage range is 0-2V for diode sensors (43 sensors out of 64). PtCo sensors have 0-150mV range (21 sensors out of 64).