The HEF4538BT.652 is a type of digital logic chip made by NXP Semiconductors. It is a monostable multivibrator circuit with two inputs (trigger and reset) and one output. It is a dual-in-line package containing two independent monostable multivibrator circuits. The HEF4538BT.652 is used for many applications like frequency division, timer pulse generation, pulse detection, and oscillator circuits. It is built using NXP's high-speed CMOS technology allowing for fast switching times and very low power consumption. The data sheet for this part can be found on the NXP website.