• Input from mechanical contact or Open Collector
• Start/Stop and Reset inputs from mechanical contact or AC voltage
• Configurable as Timer or Counter
• Five time bases, 1msec resolution
• Five ranges of counter prescaler
• Quartz timer

The catalogues of timers and counters are often packed with different models and versions: the 550 offers one model for every application.
By limiting the number of faceplate keys to those strictly necessary, there is a larger space for the display.
The miniaturisation achieved with SMT reduces the dimensions and increases the reliability.
The microprocessor enables the required performance to be selected, by means of setting only three parameters (Typ, out, in.2) by following the configuration described later.
There are two settings SP1 and SP2, five time bases: from hundredths of a second to hours and minutes, five prescaler ranges for the counter.