Delay lines are devices used to slow down a signal by a time interval in an electrical network. There are two basic delay line technologies: passive and active. Passive delay lines or analog delay lines (ADL) are built with analog components and can delay both analog and digital signals. They attenuate the signal from input to output and use components such as capacitors and inductors. Active delay lines or digital delay lines (DDL) are built with digital components and are used to delay only digital signals. Active delay lines do not attenuate the signal from input to output, and are characterized by a specific logic family. Common logic families include transistor-transistor logic (TTL), complementary metal-oxide semiconductor (CMOS), and emitter-coupled logic (ECL).