HP50 How to turn on or off some indicators ?

[sunhp]

At the address #0010Ch there is a nibble, and the value of its bits can
be used to turn on or off some indicators:
bit number function
0 busy indicator (1=on, 0=off)
1 transmit indicator (1=on, 0=off)
2 ?
3 show indicators? (1=on, 0=off)
So if I want to turn off the busy indicator, I have to read the nibble
at #0010C, turn its bits 0 to 0, and then leave.

Well it does nothing on HP 50g, does anybody know how to turn off indicators on this calc ?

Thanks,
sunhp