sermctl
int sermctl(dev_t dev, int, int);
(void)sermctl(dev, TIOCM_DTR, DMSET);
(void)sermctl(tp->t_dev, TIOCM_DTR, DMBIC);
(void) sermctl(dev, TIOCM_DTR, DMBIS);
(void) sermctl(dev, TIOCM_DTR, DMBIC);
(void) sermctl(dev, *(int *) data, DMSET);
(void) sermctl(dev, *(int *) data, DMBIS);
(void) sermctl(dev, *(int *) data, DMBIC);
*(int *)data = sermctl(dev, 0, DMGET);
(void)sermctl(tp->t_dev, 0, DMSET); /* hang up line */
(void)sermctl(tp->t_dev, TIOCM_DTR, DMSET);