The LISA Technology Package (LTP) phase meter unit is an element of the LTP optical metrology subsystem. This unit detects the interferometric opto-electrical signals from photodiodes on the optical bench interferometers, converts analog to digital signals and calculates Fourier transformed (FT) data from the electrical raw digital data. These FT data encode the positions and attitudes of the test masses which will be determined using the FT data by post-processing inside the data management unit.