hearing person by an audio link. VRI can be used for situations in which no on-site interpreters are available. However, VRI cannot be used for situations in which all parties are speaking via telephone alone. With video relay service (VRS), the sign language user, the interpreter, and the hearing person are in three separate locations, thus allowing the two clients to talk to each other on the phone through the interpreter. With recent developments in artificial intelligence in computer science, some recent deep learning based machine translation algorithms have been developed which automatically translate short videos containing sign language sentences (often simple sentence consists of only one clause) directly to written language. Sign Union flag The Sign Union flag was designed by Arnaud Balard. After studying flags around the world and vexillology principles for two years, Balard revealed the design of the flag, featuring the stylized outline of a hand. The three colors which make up the flag design are representative of Deafhood and humanity (dark blue), sign language (turquoise), and enlightenment and hope (yellow). Balard intended the flag to be an international symbol which welcomes deaf people. Language endangerment and extinction As with any spoken language, sign languages are also vulnerable to becoming endangered. For example, a sign language used by a small community may be endangered and even abandoned as users shift to a sign language used by a larger community, as has happened with Hawai'i Sign Language, which is almost extinct except for a few elderly signers. Even nationally recognised sign languages can be endangered; for example, New Zealand Sign Language is losing users. Methods are being developed to assess the language vitality of sign languages. Endangered sign languages Adamorobe Sign Language (AdaSL) Ban Khor Sign Language (BKSL) Benkala Sign Language (KK) Finland-Swedish Sign Language (FinSSL) Hawai'i Sign Language (HPSL) Inuit Sign Language (IUR) Jamaican Country Sign Language (KS) Maritime Sign Language (MSL) Old Bangkok Sign Language (OBSL) Old Chiangmai Sign Language (OCSL) Plains Indian Sign Language (PISL) Providencia Sign Language (PSL) Rennellese Sign Language (RSL) Extinct sign languages Angami Naga Sign Language Belgian Sign Language (BGT) Henniker Sign Language Martha's Vineyard Sign Language (MVSL) Ngarrindjeri sign language Old French Sign Language (VLSF) Old Kentish Sign Language (OKSL) Pitta Pitta sign language Plateau Sign Language Sandy River Valley Sign Language Warluwarra sign language Communication systems similar to sign language There are a number of communication systems that