Information processing
ISO 1745:1975 Information processing – Basic mode control procedures for data communication systems is an early ISO standard defining a Telex-oriented communications protocol that used the non-printable ASCII transmission control characters SOH (Start of Heading), STX (Start of Text), ETX (End of Text), EOT (End of Transmission), ENQ (Enquiry), ACK (Acknowledge), DLE (Data Link Escape), NAK (Negative Acknowledge), SYN (Synchronous Idle), and ETB (End of Transmission Block).