Siemens alarm 400262: Failure of handheld unit
SINUMERIK PLC system alarm · Siemens 840D/810D powerline
What it means
The handheld unit (HHU) on the dedicated handheld interface failed to answer within the FB1 HHUTimeout monitoring window, so the PLC flags the operator device as failed. Handwheel and axis-selection functions of the HHU are unavailable while the alarm stands. Connection, supply and the FB1 timing parameters have to be verified.
Likely causes
- HHU connection cable damaged or unplugged
- HHU not powered (external 24 V or interface supply)
- FB1 HHUTimeout too short / HHUCycl changed from default
- Faulty handheld unit electronics
Triage note: Program continuation: internal. Related: 400266 pointer-parameter and 400270 communication-error alarms for the HHU.
Need the part urgently?
Send us alarm 400262 with your machine details — typical RFQ turnaround is 24–48h.