An autopen or signing machine is a device used for the automatic signing of a signature or autograph. Many celebrities, politicians and public figures receive hundreds of letters a day, many of which request a personal reply; this leads to a situation in which either the individual must artificially reproduce their signature or heavily limit the number of recipients who receive a personal response. Given the exact verisimilitude to the real hand signature, the use of the autopen allows for a small degree of wishful thinking and plausible deniability as to whether a famous autograph is real or reproduced, thus increasing the perception of the personal value of the signature by the lay recipient. However, known or suspected autopen signatures are also vastly less valuable as philographic collectibles; legitimate hand-signed documents from individuals known to also use an autopen usually require verification and provenance to be considered valid.
The early autopens used a plastic matrix of the original signature which is a channel cut into an engraved plate in the shape of a wheel. A stylus driven by an electric motor followed the x and y axis of a profile or shape engraved in the plate (which is why it is called a matrix). The stylus is mechanically connected to an arm which can hold almost any common writing instrument, so the favourite pen and ink can be used to suggest authenticity. The Autopen signature is made with even pressure (and indentation in the paper), which is how these machines are distinguishable from original handwriting where the pressure varies.
Modern day autopens use a signature smart card or USB flash drive to store signatures and phrases instead of the plastic matrices. In addition, certain models can replicate entire pages of writing once a custom font has been created in a user's handwriting.
The first signature duplicating machines were developed by an Englishman named John Isaac Hawkins. Hawkins received a United States patent for his device in 1803. In 1804, Thomas Jefferson began using the device extensively. This early device was known at the time as a polygraph (an abstracted version of the pantograph) and bears little resemblance to today's autopens in design or operation. The autopen called the Robot Pen was developed in the 1930s, and became commercially available in 1937 (used as a storage unit device, similar in principle to how vinyl records store information) to record a signer's signature. A small segment of the record could be removed and stored elsewhere to prevent misuse. The machine would then be able to mass-produce a template signature when needed.
While the Robot Pen was commercially available, the first commercially successful autopen was developed by Robert M. De Shazo, Jr., in 1942. De Shazo developed the technology that became the modern autopen in reference to a Request For Quote (RFQ) from the Navy, and in 1942, received an order for the machine from the Secretary of the Navy. This was the beginning of a significant market in government for the autopen, as the machines soon ended up in the offices of members of Congress, the Senate and the Executive branches. At one point, De Shazo estimated there were more than 500 autopens in use in Washington, D.C.
Confidentiality is extremely important to autopen owners and most will not divulge whether they own one or not. Some say Harry Truman was the first United States President to use the Autopen as a way of responding to mail and signing checks. Others credit Gerald Ford as the first President to openly acknowledge his use of the Autopen, but Lyndon Johnson allowed photographs of his autopen to be taken while he was in office, and in 1968 the National Enquirer ran them along with the front-page headline "The Robot That Sits In For The President." 
Autopen devices are used today by politicians and fundraisers to sign letters to constituents written by administrative assistants and clerical staff, and by other famous people to sign autographs.
While visiting France, US President Barack Obama authorized the use of an autopen to create his signature which signed into law an extension of three provisions of the USA PATRIOT Act. On January 3, 2013, he signed the extension to the Bush tax cuts, using the Autopen while vacationing in Hawaii. In order to sign it by the required deadline, his other alternative would have been to have had the bill flown to him overnight. Republican leaders have questioned whether this use of the Autopen meets the Constitutional requirement for signing a bill into law, but the validity of presidential use of an autopen has not been actually tested in court. During his term in office, President George W. Bush asked for and received a favorable opinion from the Department of Justice regarding the constitutionality of using the autopen, but did not use it himself.
Further developing the class of devices known as autopens, Canadian author Margaret Atwood created a device called the Longpen, which allows audio and video conversation between the fan and author while a book is being signed remotely.