HP75D and data acquisition unit HP3421A

[hesc]

Dear all,

In my HP75C a data communications ROM is installed, 00075-15035. In my other HP75D I see 2 empty slots and the third one is occupied by a rather large tele communications unit around the HP75D, I believe.
So, I think indeed, the missing IO module in both HP's may be the problem...

Thank you all for solving the problem.

Kind regards,

Henk