2010 ADA Standards for Accessible Design Pocket Guide
TTYs required at a public pay telephone shall be permanently affixed within, or adjacent to, the telephone enclosure. Where an acoustic coupler is used, the telephone cord shall be sufficiently long to allow connection of the TTY and the telephone receiver.
When in use, the touch surface of TTY keypads shall be 34 inches (865 mm) minimum above the finish floor. [S.H. 4.31.9(2)]
EXCEPTION: Where seats are provided, TTYs shall not be required to comply with 704.4.1.
Advisory 704.4.1 Height. A telephone with a TTY installed underneath cannot also be a wheelchair accessible telephone because the required 34 inches (865 mm) minimum keypad height can causes the highest operable part of the telephone, usually the coin slot, to exceed the maximum permitted side and forward reach ranges. (See Section 308).
Advisory 704.4.1 Height Exception. While seats are not required at TTYs, reading and typing at a TTY is more suited to sitting than standing. Facilities that often provide seats at TTY’s include, but are not limited to, airports and other passenger terminals or stations, courts, art galleries, and convention centers.