Roland Saur-Brosch

I have a 2611B connected via a Keysight Technologies 82357B USB to GPIB adapter.

I'd like to communicate with the 2611B using low level GPIB commands, possibly without some other additional layer.
I have a small routine that just sends the command over GPIB and receives a string, but I first tried to use the Keysight Interactive IO tool.

If I send

*IDN?

I receive

Keithley Instruments Inc., Model 2611B, 4038432, 3.0.3

so the connection itself should work.

But even simple commands like

:SYSTem:LFRequency?

just result in a timeout.

 ! VI_ERROR_TMO: A timeout occurred
Visa ErrorCode: 0xBFFF0015 (-1073807339)

Can somebody tell me how to make the 2611B respond to my requests?

Thanks!