TTL signals allow to perform pump/probe experiments or fluorescence measurements with short laser pulses in a controlled and reproducible manner.
Using a board by National Instruments connected to a PC, up to seven TTL channels can be defined. With appropriate settings for duration and delay times, advanced experiments can be performed, e.g., involving multiple lasers, shutters, etc.
The TTL signals are set up through a LabView interface called "Clock7.exe" running on computer rita.