From 2018, aircraft with an MTOW >5700 kg or max cruise speed > 250 Kts will have to send BPS on ADS-B.
For Mode S I don't know the regulations by heart, but if I remember correctly, EHS is at the moment mandatory in some countries for certain aircraft categories.
What information are you looking for? Do you need information on specific transponder models or are you looking for certification standards, mandates etc.