Telephony and infrastructure

Audio codecs

An audio codec is the scheme that squeezes sound into a form a network can carry, and whichever one a voice system runs on settles how the audio sounds, what it costs in bandwidth, and how much of it a recognizer can actually transcribe.

Concurrency

Concurrency counts the conversations a voice system can run at once, which makes it a question about capacity rather than about volume, and it governs what happens on the busiest day instead of the ordinary one.

DTMF

DTMF, dual-tone multi-frequency, is the touch-tone scheme that turns every keypad press into its own pair of tones, and it remains the right way to collect the card numbers, PINs and reference codes that speech recognition reliably mangles.

PSTN

The PSTN, or Public Switched Telephone Network, is the worldwide arrangement of carriers, numbering plans and interconnect deals that lets any phone number dial any other, and the narrowband audio it carries holds measurably less information than a browser microphone captures.

SIP and SIP trunking

SIP, the Session Initiation Protocol, is what phone systems use to open, manage and close voice calls across internet networks, and SIP trunking is the service you buy to reach the outside telephone network through an internet connection rather than through physical lines into the building.

STIR/SHAKEN and spam-likely labeling

STIR/SHAKEN is a framework that lets carriers cryptographically verify a call really originates from the number it claims, while spam-likely labeling is a separate and proprietary scoring layer that decides whether a warning appears on the recipient screen.

WebRTC

WebRTC is a set of open browser standards for capturing, processing and transporting live audio and video in real time, and it is what lets a website hold a spoken conversation with no plugin, no app and no phone call.