Refers to the ITU specification for fax machines that use digital encoding. Encoding methods for Group 3 fax machines include MH (Modified Huffman), MR (Modified Read) and MMR (Modified Modified Read). If a fax is said to be "Group 3 compatible" this means that the unit will communicate with virtually all other installed fax machines. A Group 3 fax machine equipped with a 33.6 Kbps modem can transmit a page at 3 seconds per page (based on the ITU-T Test Chart #1 in Standard resolution, and not including the handshake). Older analog Group 1 and Group 2 fax machines are obsolete.