Well the whole idea of samizdat was based on the access to a typewriter. Not necessarily at home, my mom was a librarian and she would use the typewriter in her office to type books.
And the reason for typewriter control is that typewriters are somewhat unique; all the typewriters used to be registered (i.e. the security services have their writing samples together with the owner/location of the device) so that if a particularly unwanted type of samizdat (e.g. actual political agitation) was detected then they could and would determine that this was typed on the typewriter in your mom's office and go in and determine who participated in making these copies.
