Designations that notify the MCS (message control system) that a specific condition exists such as end-of-group, end-of-message, or end-of-segment. There are three types of message indicators: EGI, end-of-group indicator; EMI, end-of-message indicator; and ESI, end-of-segment indicator.; 一些符號,通知報文控制系統(tǒng)一個指定的條件成立, 如組結(jié)束、報文結(jié)束或段結(jié)束等。有三種類型的報文指示符: EGI, 組結(jié)束指示符;EMI，報 文結(jié)束指示符；ESI,段結(jié)束指示符。