A central office (CO) for a telephone connected with a telecommunication device for the deaf (TDD) called by a calling device determines that the called TDD is connected with the called CO. The called CO postpones indication that the called TDD has connected with the called CO, until the called CO determines...http://www.google.com/patents/US6560317?utm_source=gb-gplus-sharePatent US6560317 - Receiving caller identification information with a telecommunications device for the deaf
