Building Automation Level II Practice Exam

DTMF, or Dual-Tone Multi-Frequency signaling, is designed to carry commands over voice-grade telephone lines. When a keypad is pressed, two tones are generated that encode the digit, and the receiving controller decodes those tones to execute the command. This makes it well-suited for remotely controlling building systems like security and CCTV over dial-up lines. Infrared requires line-of-sight and short range, Bluetooth is even more limited in distance, and Wi‑Fi relies on a local network rather than a dial-up voice channel, so they aren’t appropriate for dial-up control.