Electrical and mechanical interface characteristics and line control protocol using communication control characters for serial data link between a direct numerical control system and numerical control equipment employing asynchronous full duplex transmission 電子和機械界面特性和在直接數(shù)字控制系統(tǒng)與用同步完全雙向傳輸?shù)臄?shù)字控制設(shè)備之間的系列數(shù)據(jù)鏈接的通信控制字符的線路控制協(xié)議