Can I connect several Three-color Universal Indicator ITP17 to the common analog output? How should I connect them, in series or in parallel?

Yes, you can do this.
The connection depends on the input signal:
- Current (4-20 mA, 0-5 mA or 0-20 mA) – serial connection; the maximum number of displays depends on the available power, each ITP17 consumes 1W;
- Voltage (0-10 V or 2-10 V) – parallel connection; the maximum number of displays depends on the available load current.