Type Alias: LtpPhase

LtpPhase = "neutral" | "transfer"

The protocol phase. The line is either neutral (idle - awaiting an ENQ to establish, or reset there after an EOT) or in transfer (establishment accepted; frames and their per-frame ACK/NAK flow until the sender's EOT). The classic three-phase LIS01 model (establishment → transfer → termination) collapses to these two, since establishment is the neutral → transfer edge and termination is the transfer → neutral edge.