Transaction Network, Telephones, and Terminals: Dial Access Interface

The three Dial-In protocols in Transaction Network (TN) range from a simple protocol with no transmission error recovery capabilities to a more complex protocol which includes error recovery and rigorous checks for transmission irregularities between the telephone and the TN message switch (MS). The simplest, the Voice Response protocol, uses audioprompting messages for input error correction and only audio responses from the message switch. The Voice/Keyed Answer Tone (KAT) protocol employs no error-correcting facility, but can be used with automatic telephones that transmit control sequences, some of which help detect transmission errors. The types of responses from the Customer Service Center (CSC) that are allowed in the Voice/KAT protocol are either a Keyed Answer Tone by itself or in combination with a voice message. Last is the Data Response protocol which has a facility for transmission error correction and whose responses from the message switch use frequency-shift keying (FSK). Once access to the MS has been established, 1 the user may enter single or multiple inquiries before a response message is received. This, in fact, may be necessary if the CSC requires a message whose length exceeds the TN maximum of 128 characters. Although multiple inquiries with a single 3441