Editing Chess clock (section)

== Designs ==

=== Analog game clocks ===
[[File:Garde Schachuhr 1.jpg|thumb|A typical analog chess clock]]

[[Analog clock]]s are equipped with a "flag" that falls to indicate the exact moment the player's time has expired. Analog clocks use mechanical buttons. Pressing the button on one player's side physically stops the movement of that player's clock and releases the hold on the opponent's.

The drawbacks of the mechanical clocks include accuracy and matching of the two clocks, and matching of the indicators (flags) of time expiration. Additional time cannot easily be added for more complex time controls, especially those that call for an increment or delay on every move, such as some forms of [[byoyomi]].

=== Early development of digital game clocks ===
[[File:DGT 2010 digital chess clock.ajb.jpg|alt=A brown chess clock with blue buttons along the bottom. A digital display shows the time remaining for each side|thumb|Digital chess clock]]
In 1973, to address the issues with analog clocks, [[Bruce Cheney]], a [[Cornell University]] electrical engineering (EE) student and chess player, created the first digital chess clock as a project for an undergraduate EE course.<ref>"Early Bird", ''[[Chess Life]]'', April 1992.</ref> Typical of most inventions, it was crude compared to the products on the market many years later and was limited by the technology that existed at the time. For example, the display was implemented via red LEDs, which required significant power and, as a result, the clock had to be plugged into a wall outlet. The high cost of LEDs at the time meant that only one set of digits could be displayed: that of the player whose turn it was to move. This meant that each player's time had to be multiplexed to the display when their time was running. In 1973, [[Large-Scale Integration#SSI, MSI and LSI|LSI]] chips were not readily or cheaply available, so all the multiplexing and logic was enabled using chips consisting of four two-input [[Transistor–transistor logic|TTL NAND gates]], resulting in excessive power consumption. Being plugged into the wall is obviously a major drawback, but had one advantage: [[Utility frequency#Stability|the timebase for the clock was driven off a rectified version of the alternating current mains frequency]]. Each player had a separate counter and, in a parallel to the original mechanical architecture, one player's counter was disabled while the other's was running. The clock only had one mode: time ran forward. It could be reset, but not set. It did not count the number of moves. But it successfully addressed the original goals of the project (accurate and matched timing).

The first commercially available digital chess clock was patented in 1975 by Joseph Meshi and Jeffrey R. Ponsor. They named it the Micromate-80.<ref>{{cite patent |country=US |number=4062180 |status=patent |title=Electronic chess clock |gdate= 1977-12-13 |fdate= 1975-07-31 |invent1= Meshi, Joseph |invent2= Ponsor, Jeffrey R.}}; filed July 1975.</ref> There was only one made<ref>{{Cite web|title=Chess clock - Rules and strategy of chess games|url=http://gambiter.com/chess/chess_clock.html|access-date=2020-10-15|website=gambiter.com}}</ref> and this was tested by chess players in multiple tournaments. Three years later a much-improved Micromate-180 was produced alongside Meshi's MBA [[thesis]], "Demand Analysis for a New Product (The Digital Chess Clock)", at [[San Diego State University]], while Meshi and Ponsor continued to develop digital gaming.<ref name=":0">{{cite patent |country=US |number=4247925 |status=patent |title=Game microcomputer |gdate= 1981-01-27 |fdate= 1978-07-13 |invent1= Meshi, Joseph |invent2= Ponsor, Jeffrey R.}}; filed January 1978.</ref>

=== Fischer clock and related designs {{anchor|Fischer clock}} ===
[[Image:Olimpiada Bled Slovenija deska.jpg|thumb|Digital chess clock connected to a board that automatically senses when moves have been made.]]
Digital clocks and Internet gaming have spurred a wave of experimentation with more varied and complex time controls than the traditional standards. [[Time control]] is commonly used in modern chess in many different [[Time control#Methodology|methodologies]]. One particularly notable development, which has gained quite wide acceptance in chess, was proposed by former world champion [[Bobby Fischer]], who in 1988 filed for US patent 4,884,255 (awarded in 1989) for a new type of digital chess clock. Fischer's digital clock gave each player a fixed period of time at the start of the game and then added a small amount after each move.<ref name=":1">{{cite patent |country=US |number=4884255|status=patent |title=Digital chess clock |gdate= November 28, 1989|pridate=August 5, 1988|fdate= August 5, 1988|invent1= Fisher, Robert J.}}, filed August 5, 1988.</ref> Joseph Meshi called this "Accumulation" as it was a main feature of his patented Micromate-180 (US Patent 4,247,925 1978).<ref name=":0" />

The increment time control was first used in the privately organised [[Fischer–Spassky (1992 match)|1992 Fischer–Spassky match]], and quickly became popular in the wider chess world, being subsequently used in the [[FIDE World Chess Championship 1998]].<ref>[http://theweekinchess.com/html/twic161.html The Week in Chess 161], [[The Week in Chess]], 8-Dec-1997</ref> Nowadays most top level tournaments and tournaments outside the United States use Fischer's system. An increasing number of lower level tournaments in the US are also starting to use Fischer's system. Other aspects of Fischer's patent, such as a synthesized voice announcing how much time the players have, thus eliminating the need for them to keep looking at the clock, have not been adopted.<ref name=":1" />

On March 10, 1994, a patent application was filed by inventors Frank A. Camaratta Jr. of Huntsville, Alabama, and William Goichberg of Salisbury Mills, New York, for a game timer especially suitable for playing the game of chess, which employed a (simple) "delay" feature. The game timer provides, among other features, a user-definable delay between the time the activation button is pressed and the time that the activated clock actually begins to count down. United States Patent 5,420,830 was issued on May 10, 1995, and subsequently assigned to the United States Chess Federation by the inventors. As with the Fischer clock, the benefit of the delay clock is to reduce the likelihood that a player with positional or material superiority will lose a match solely because of the expiration of time on that player's time clock.<ref>{{Cite patent|number=US5420830A|title=Chess clock|gdate=1995-05-30|invent1=Jr|invent2=Goichberg|inventor1-first=Frank A. Camaratta|inventor2-first=William|url=https://patents.google.com/patent/US5420830/en}}</ref> In the United States, delay is still widely used, but increment is becoming more popular.<ref>{{Cite web |date=2021-09-28 |title=Rule Book Updates and Changes |url=https://new.uschess.org/rule-book-updates-and-changes |access-date=2023-07-15 |website=US Chess.org |language=en}}</ref>