Date   : Tue, 20 Mar 1984 21:59:00-EST
From   : Robert L. Plouffe <PLOUFF@mit-mc>
Subject: PMMI ring-back fixed

Message forwarded from Irv Hoff to fix the PMMI ring-back
function in MDM727-729.

 #: 83977      Sec. 0 - Communications
Sb: #PMMI problem fixed
    20-Mar-84  06:48:04
Fm: Irv Hoff   72365,70
To: Bob Plouffe 70220,113 (X)

Found the problem with the PMMI ringback.  My fault.  When I fixed MDM727 for
(0-9) numbers on redialing, and renumbered some labels, missed this one. 
However, it's still a bit of a flakey circuit, as we wait 7 seconds after
dialing, hope it goes through all the exchanges and has rung once, then we hang
up, wait 5 seconds and go back and redial.

Call this MDM727-9.MOD


SUBJECT :  MDM727 - MDM729  MOD FOR PMMI USERS FOR RINGBACK NUMBERS

FROM    :  IRV HOFF W6FFC

DATE    :  18 MAR 84


       This mod affects just PMMI modems that are using MDM727 and
       later, including MDM728 or MDM729.  Change one byte:

             097F  from 75  to  69       (then SAVE 73 sectors)

       The ringback circuit should then work normally.  When I fixed
       MDM727 to allow redialing the new (0-9) numbers and changed some
       some labels, this one was overlooked, sorry.   If changing the
       source code, make the following change:
;.....
;
;
; Hang up, redial and listen for dial tone
;
RINGBK1: CALL   HANGUP          ;hang up the phone
         MVI    B,RBWAIT        ;wait 5 seconds before redialing..
         CALL   TIMER           ;..for line to clear, etc.
         CALL   DIALBGN         ;disconnect, reconnect, wait for tone
         JNC    DIAL12          ;go redial number
         JMP    DIALAGN         ;no dial tone heard
;.....
;
-    -    -    -    -    -    -    -    -    -    -    -    -    -    -

(next to last line was:    JNC   DIAL13    which was incorrect)