The following Standard is an optional extension of the Standard ECMA- 16 on Basic Mode Control Procedures for Data Communication Systems.
This means that:
i) those systems which conform to Standard ECMA-16 do not necessarily have to include the functions described in the present Standard,
ii) systems implementing the function described hereafter must comply with the present Standard to conform to Standard ECMA-16 on Basic Mode Control Procedures.
This Standard specifies recovery procedures to be executed by the various stations on a data transmission link to automatically return the system to an operational status after a fault condition has occured. It is based upon recovery procedures defined in ECMA-16, section 2.3-.3.
These procedures are system guidelines which should be used by all stations, as applicable. It is recognized that the implementation of the timers and counters and their absolute value may vary with applications and communication facilities and that a given timer can cover more than one function.
In some cases, these recovery procedures can only detect the abnormal condition and then notify the operator or the processor program or both. In more sophisticated .cases, automatic recovery is partially or completely possible.
In other cases, only operators can perform the recovery procedures. However, the operator may do such things as retry “N” more times, establish voice communications to the distant station in order to determine trouble, etc.
For a good system, the functions of Timers A, B and C defined below, must be utilized. It is recognized that in some systems additional timers may be required for such purposes as aiding synchronization procedures and added reliability, etc.