MCR_OUT2
#define PTT_ON (MCR_RTS|MCR_OUT2) /* activate PTT */
#define PTT_OFF (MCR_DTR|MCR_OUT2) /* release PTT */
outb(MCR_OUT1 | MCR_OUT2, MCR(iobase));
outb(MCR_DTR | MCR_RTS | MCR_OUT1 | MCR_OUT2, MCR(iobase));
outb(bit | MCR_OUT1 | MCR_OUT2, MCR(iobase));