A telephone keypad is a keypad installed on a push-button telephone or similar telecommunication device for dialing a telephone number. It was standardized when the dual-tone multi-frequency signaling (DTMF) system was developed in the Bell System in the United States in the 1960s that replaced rotary dialing originally developed in electromechanical switching systems. Because of the installed abundance of rotary dial equipment well into the 1990s, many telephone keypads were also designed to produce loop-disconnect pulses electronically, and some could be optionally switched to produce either DTMF or pulses.

The development of the modern telephone keypad is attributed to research in the 1950s by Richard Deininger under the directorship of John Karlin at the Human Factors Engineering Department of Bell Labs. The modern keypad is laid out in a rectangular array of twelve push buttons arranged as four rows and three columns of keys. For military applications, a fourth, right-most column of keys was added for priority signaling in the Autovon system in the 1960s. Initially, between 1963 and 1968, the keypads for civilian subscriber service omitting the lower left and lower right keys that commonly are assigned to the star (✻) and number sign (#) signals, respectively. These keys were added to provide signals for anticipated data entry purposes in business applications, but found use in Custom Calling Services (CLASS) features installed in electronic switching systems. (Full article...)

A satellite telephone, satellite phone or satphone is a type of mobile phone that connects to other phones or the telephone network by radio link through satellites orbiting the Earth instead of terrestrial cell sites, as cellphones do. Therefore, they can work in most geographic locations on the Earth's surface, as long as open sky and the line-of-sight between the phone and the satellite are provided. Depending on the architecture of a particular system, coverage may include the entire Earth or only specific regions. Satellite phones provide similar functionality to terrestrial mobile telephones; voice calling, text messaging, and low-bandwidth Internet access are supported through most systems. The advantage of a satellite phone is that it can be used in such regions where local terrestrial communication infrastructures, such as landline and cellular networks, are not available.

Satellite phones are popular on expeditions into remote locations where there is no reliable cellular service, such as recreational hiking, hunting, fishing, and boating trips, as well as for business purposes, such as mining locations and maritime shipping. Satellite phones rarely get disrupted by natural disasters on Earth or human actions such as war, so they have proven to be dependable communication tools in emergency and humanitarian situations, when the local communications system have been compromised.

The mobile equipment, also known as a terminal, varies widely. Early satellite phone handsets had a size and weight comparable to that of a late-1980s or early-1990s mobile phone, but usually with a large retractable antenna. More recent satellite phones are similar in size to a regular mobile phone while some prototype satellite phones have no distinguishable difference from an ordinary smartphone. (Full article...)

Dual-tone multi-frequency signaling (DTMF) is a telecommunication signaling system using the voice-frequency band over telephone lines between telephone equipment and other communications devices and switching centers. DTMF was first developed in the Bell System in the United States, and became known under the trademark Touch-Tone for use in push-button telephones supplied to telephone customers, starting in 1963. DTMF is standardized as ITU-T Recommendation Q.23. It is also known in the UK as MF4. (Full article...)

John Thomas Draper (born March 11, 1943), also known as Captain Crunch, Crunch, or Crunchman (after the Cap'n Crunch breakfast cereal mascot), is an American computer programmer and former phone phreak. He is a widely known figure within the computer programming world and the hacker and security community, and generally lives a nomadic lifestyle. (Full article...)