Telephony

/ˌeɪ ˈɛm/

noun … “sending sound by stretching and shrinking a carrier wave.”

AM, short for Amplitude Modulation, is a method of encoding information onto a carrier wave by varying its amplitude while keeping the frequency and phase constant. Unlike FM or digital modulation schemes such as QPSK, AM directly scales the voltage of the carrier signal in proportion to the instantaneous value of the message signal, typically audio or telemetry data.

The core characteristics of AM include a carrier signal, sidebands (upper and lower), and susceptibility to noise, since amplitude variations caused by interference affect the transmitted signal. The modulated signal can be represented mathematically as V(t) = [1 + m(t)] * cos(2πfct), where m(t) is the message signal normalized to 1, and fc is the carrier frequency.

In practice, AM is used in broadcasting (e.g., AM radio), aviation communications, and legacy telemetry systems. A transmitter takes the audio signal, modulates a high-frequency carrier, and sends it through an antenna. The receiver demodulates by extracting amplitude variations to reconstruct the original message.

Conceptually, think of AM as a flexible canvas: the carrier wave is a steady brushstroke, and the message signal paints over it with varying intensity, creating a waveform that can travel long distances but is sensitive to smudges—i.e., noise.

/ˈvɔɪp/

n. “Your phone, but over the internet instead of wires.”

VoIP, or Voice over Internet Protocol, is a technology that allows voice communications and multimedia sessions to be transmitted over IP networks, such as the internet, rather than traditional circuit-switched telephone lines. It converts analog audio signals into digital data packets, sends them over a network, and then reassembles them into sound at the receiving end, enabling phone calls, video calls, and conferencing entirely online.

Unlike legacy telephony, VoIP leverages the flexibility of networks, allowing features like call routing, voicemail-to-email, integration with software applications, and even encryption. Modern implementations often use protocols like SIP (Session Initiation Protocol) or H.323 to establish and manage calls efficiently, while codecs such as G.711, G.722, or Opus determine the quality of transmitted audio.

VoIP offers numerous advantages: cost savings, especially for long-distance or international calls; scalability for businesses; and integration with cloud services and collaboration tools. Popular examples include platforms like Zoom, Microsoft Teams, and Cisco Webex, all of which rely heavily on VoIP technologies to deliver real-time voice and video communication.

Security is a critical aspect of VoIP. Since calls are transmitted as digital packets, they are susceptible to interception, eavesdropping, and tampering. Techniques involving HMAC, encryption with SHA256, or TLS (Transport Layer Security) are often applied to protect the integrity and privacy of communications. Network monitoring and proper firewall configurations are essential to mitigate risks like toll fraud, spoofing, or DDoS attacks.

A practical example: a small business can replace traditional phone lines with VoIP, allowing employees to make calls from laptops, smartphones, or desk phones over the company’s internet connection. Advanced features like auto-attendants, call forwarding, and voicemail transcription improve operational efficiency while reducing costs.

In summary, VoIP transforms how we communicate by harnessing the internet for real-time voice and multimedia delivery. It bridges traditional telephony with modern networked environments, offering flexibility, cost efficiency, and integration capabilities, while requiring awareness of cybersecurity practices to ensure safe and reliable communication.