USS Hathaway firing at the USS Enterprise-D with laser pulses
A laser pulse system fires a laser beam through a starship's weapons array. This modification to a starship's weapons system allows for simulated phaser and photon torpedo operation and performance, but with no potential for actual damage. The system is used to record hits in Starfleet battle simulations without risking damage to the ships involved.
In 2365, the USS Enterprise-D's primary weapons were disconnected and hooked up to a laser pulse system in order to participate in a training exercise with the USS Hathaway, which was similarly outfitted. Unfortunately, during the exercise the Enterprise was attacked by the Ferengi vessel Kreechta, fusing the connections to the laser pulse system. The laser system could not be disengaged, meaning that the Enterprise could not return fire with normal weapons. (TNG: "Peak Performance")