Data repeating apparatus

Abstract

In a communication network system such as a local area network (i.e., LAN), a plurality of repeating stations each providing a data repeating apparatus are linked together by a transmission line, wherein serial data of which significant data portion is sandwiched by delimiters is transferred. This serial data is received and repeated by the data repeating apparatus, from which it is sent out to the next station. When detecting the delimiter, this apparatus produces a delimiter timing signal. On the basis of this delimiter timing signal, a first conversion timing signal synchronized with the receiving clock is generated, while a second conversion timing signal synchronized with the sending clock is also generated. The receiving serial data is temporarily converted into parallel data by the first conversion timing signal, and then, this parallel data is re-converted into serial data by the second conversion timing signal. This serial data is sent out from the repeating station. Herein, a preamble portion (i.e., invalid-bit portion) is automatically formed on the basis of the maximum number of the drop-out bits corresponding to the number of the repeating stations linked together by the transmission line, so that this preamble portion is sent out with the re-converted serial data. When a period difference between the first and second conversion timing signals exceeds the predetermined allowable value, the bit-conversion size (e.g., 8 bits or 16 bits) is changed so as to avoid the bit-overflow phenomenon.