diff --git a/PDP11/pdp11_dz.c b/PDP11/pdp11_dz.c
index c9e7ddad..bf54e455 100644
--- a/PDP11/pdp11_dz.c
+++ b/PDP11/pdp11_dz.c
@@ -590,6 +590,7 @@ t_stat dz_xmt_svc (UNIT *uptr)
 {
 tmxr_poll_tx (&dz_desc);                                /* poll output */
 dz_update_xmti ();                                      /* update int */
+sim_clock_coschedule_after (uptr, 500000);              /* reactivate occasionally */
 return SCPE_OK;
 }