24 10BT ports standard. Somewhat modular, can be re-configured to use BNC ports. One AUI port. Expansion hubs also have AUI ports. RS-232 connection on back of base hubs only.
All hubs have slots on the top to accept expansion hubs.
Expansion hubs have cards on the bottom to fit these slots. Keep un-used slots covered with tape. 1924C-A has one 100TX and one 100FX port. Use the 100TX ports to cascade several switches in one closet. Put tape over un-used 100TX ports so folks don't accidentally use them for 10Mbit devices.