At the board a player may have an electronic device that can receive and/or transmit data (such as a mobile phone, tablet, smart watch, visual aide [such as Google Glasses], etc.) only if the device is off (not just in airplane mode), completely out of sight, and not readily accessible because it is contained in something else (such as a carrying case, jacket pocket, pants pocket, backpack, etc.).
At the board a player may not have in or around the player’s ear a device that can receive and/or transmit data (such as headphones, earbuds, etc.)—unless it is a medically approved hearing aide. A player may have in or around the player’s ear a device to block out sound (such as earplugs); however, a device such as earmuffs is forbidden, because it would be too difficult and intrusive for a tournament director to determine whether it has been electronically modified.
At the board a player may use only the following personal electronic-notation devices, because as of 2018.02.07 they are the only single-purpose personal electronic-notation devices created to serve exclusively and continuing to serve exclusively the purpose of electronic notation:
At the board a player may use a personal electronic-notation device only if, with a quick glance from 20 feet away, a tournament director can differentiate the device immediately from any mobile device that can receive and/or transmit data. 20 feet is approximately the farthest distance between a tournament director and players at their boards, as the TD walks throughout a tournament room to ensure fair play. It would be impossible for a TD to ensure both fair play and the perception of fair play, if a personal electronic-notation device were to resemble from afar a mobile device that can receive and/or transmit data. Players' concentration at the board would be disrupted unnecessarily far too frequently, if players, TDs, and/or spectators were uncertain from afar whether a player is using a personal electronic-notation device only to notate (record moves), or also to cheat.
At the board a player may not use a re-purposed personal electronic-notation device. That is, a personal electronic-notation device may not be used if it was created to serve, or if it was subsequently modified to serve any purpose other than electronic notation.
At the board a player may use a personal electronic-notation device only if it has been approved both by MD Chess and by US Chess. MD Chess reserves the right to prohibit the use of a personal electronic-notation device, even if it has been approved by US Chess. Here's the list of personal electronic-notation devices approved by US Chess as of 2017.12.18: US Chess’s Guidelines for Certification of an Electronic Scoresheet. The following list includes (but is not necessarily limited to) personal electronic-notation devices approved by US Chess, but prohibited by MD Chess: