Bull S.a.

Bull S.a. (societe Anonyme)

Christian Cabrol

Rene Baptiste

Claude Bacou

Andre Oisel

Gilbert Takats

Henri Feissel

A method and apparatus for transmission of digital data in which data words having M parallel bits are encoded into code words having N parallel bits, the code words being serially transmitted and being accompanied by flags such as Start Delimiter, End Delimeter of the frame or token. The code words and the flags are selected so as to balance the DC component. The time interval between two successive transitions of the serially transmitted signals is limited to four times the period of the serial transmission clock. For detection of errors in transmission, the Hamming distance between a flag and any encoded sequence of the same length extracted from any message is at least equal to 2. The invention is useful with transmitters and receivers that exploit the properties of the transmission method, and is applicable to data networks.

Method and apparatus for transmission of digital data

An optoelectronic transducer is proposed which includes a PIN diode (2) that delivers a current that is proportional to a light signal that is received. The diode is connected to the input of an inverting amplifier (4) that delivers a voltage signal v.sub.s. A negative feedback means of the transfer impedance type (6) is connected across the inverting amplifier. The transducer further includes a stabilizing means (8) for the amplifier gain and a temperature drift compensating means (10) for compensating for the drift in amplifier temperature. The stabilizing means (8) includes a detector (26, 28, 32) for the high peak of the signal v.sub.s, and the temperature drift compensating means (10) includes a filter means (38) for producing the means value v.sub.m of the signal v.sub.s, and a comparator (40) that receives the signals v.sub.s and v.sub.m and delivers a signal that reproduces the interference of the light signal that has been received. The temperature drift compensating (10) also includes a carrier wavedetection (cs) with automatic control (42). This automatic control enables very high speed detection of the carrier wave not only at a high level, but at a low level as well.

Optoelectric transducer

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Plaisir, France

Christian Cabrol