The Metrotek MP203 is a ultrasonic pulser plug-in for the TM500 system.
It produces a 550 V negative-going pulse with 3.2 nanoseconds fall time. This fall time was confirmed experimentally by Dennis Tillman with an MP203 pulse output coupled to a 7S11 / 7T11 / S-4 via 46 dB of attenuation (to reduce the pulse to 700 mV to protect the S-4).
Three pulse widths can be selected. The widest pulse is about 15 nanoseconds. The repetition rate is variable up to about 11.7 kHz.