On what bands may automatically controlled stations transmitting RTTY or data emissions communicate with other automatically controlled digital stations?

Automatic control means a station is transmitting without a control operator actively present at the control point. Because unattended automated digital stations can easily cause interference if left unchecked, the FCC restricts their operation to specific sub-bands. For bands 6 meters and shorter (VHF, UHF, and microwave), automated stations can operate anywhere digital modes are permitted. However, on the High Frequency (HF) bands, where propagation can carry signals globally, they are restricted to very specific, limited segments to keep them from dominating the heavily used non-phone portions.