Noise is an unwanted disturbance in electrical signals. Thermal noise is unavoidable at non-zero temperatures. Shot noise occurs when electrons flow across barriers. Flicker noise has a pink spectrum falling into higher frequencies. Burst noise creates sudden voltage/current transitions
Communications system combines interconnected networks and equipment for integrated communication. Components must serve common purpose, be technically compatible, and operate together. Telecommunications is a method of conveying meanings through signs and rules
Bandwidth is the difference between upper and lower frequencies in a continuous band. Measured in hertz (Hz). Any band of given width can carry same information regardless of location
Self-hosting enables running applications on personal servers instead of SaaS providers. List includes analytics tools like Aptabase and Matomo for data analysis. Digital archiving solutions available for websites and digital collections. Automation tools like Apache Airflow and Dagu streamline business processes
Signal is a function that conveys information about a phenomenon. Signals can be any quantity that varies over space or time. Signals are important in signal processing, information theory and biology
Voicemail systems allow callers to leave recorded messages when recipients can't answer. First public records of voice recording appeared in 1877 by Edison. Motorola Pageboy introduced in 1974 as simple pager system. IBM developed first voice-messaging application in 1973