tty, TIOCM_ST, TIOCM_SR

[openbsd_(_at_)_libkvm_(_dot_)_org]

hi, i have a question about tty ioctl()'s :

in the different state of a terminal according to
tty(4), there are TIOCM_ST TIOCM_SR which are called
secondary transmit / receive.

as far as i know, this is used only on DB25 (RS232C),
whereras DB9 (EIA/TIA 574) only has a single transmit / receive line.

why is it called *secondary* ?, does this maps only for
DB25 or does is automatically maps to RX or TX in DB9?

thank you :)

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