Many older alarm systems allow homeowners to arm or disarm their security by pressing specific DTMF key sequences during a phone call to the system. The "Hidden" Keys: A, B, C, and D
Each key is assigned a unique pair of frequencies: one low-frequency tone and one high-frequency tone. When a key is pressed, the device generates a superposition of these two sine waves. dtmf key
This report provides a comprehensive analysis of Dual-Tone Multi-Frequency (DTMF) signaling, commonly known by its legacy trademark "Touch-Tone." DTMF remains a fundamental component of the Public Switched Telephone Network (PSTN) and Voice over Internet Protocol (VoIP) infrastructures. While largely transparent to the average end-user, DTMF is critical for interactive voice response (IVR) systems and call routing. This document outlines the technical mechanics, modern applications, and significant security vulnerabilities associated with DTMF transmission. Many older alarm systems allow homeowners to arm