(* system calls available via the RSX system *)
    chaintoprog    = 47;       (* 2f command line in DMA location *)
    minstat        = 61;       (* 3d 0 for no input ready *)
    moutstat       = 62;       (* 3e 0 for output not ready *)
    mout           = 63;       (* 3f output, no ready waiting *)
    min            = 64;       (* 40 input, no ready waiting *)
    carrier        = 65;       (* 41 detected *)
    keyready       = 66;       (* 42 local console key *)
    keyinput       = 67;       (* 43   "      "     "  wait *)
    scrnout        = 68;       (* 44 to local screen only, wait *)
    sgmaxdrive     = 69;       (* 45 security system *)
    sgmaxuser      = 70;       (* 46    "        "   *)
    sgtimeout      = 71;       (* 47 inactivity disc. time, mins *)
    sgnulls        = 72;       (* 48 appended to lf, remote term *)
    sgupshift      = 73;       (* 49 remote terminal output *)
    sgcrlf         = 74;       (* 4a append lf to cr, rem. term. out *)
    sgwriting      = 75;       (* 4b disk file write in progress *)
    sghardcopy     = 76;       (* 4c remote term. input to lister *)
    sgmodemoff     = 77;       (* 4d disable remote in/out, leave on *)
    sgbellenable   = 78;       (* 4e suppress local console bells *)
    grtcbuffptr    = 79;       (* 4f real-time-clock buffer pointer *)
    gcallerptr     = 80;       (* 50 Caller id string, pointer *)
    sgmaxtimeon    = 81;       (* 51 Time on system limitations *)
    setlogintime   = 82;       (* 52 of remote caller, in rtcbuff *)
    showtimeon     = 83;       (* 53 via rtc buffer, on local screen *)
(*  sgstate        = 84;      ( * 54 Priv., terminal mode, checks *)
(*  dodelay        = 85;      ( * 55 millisecs *)
    sgbaud         = 86;       (* 56 0 enquiry, 1..10 coded rates *)
    RSX            = 87;       (* 57 master, has subcommands *)
    sgdrivector    = 88;       (* 58 bit vector of usable drives *)
    sgdate         = 89;       (* 59 set/get current date. -1 to get *)
    sgtime         = 90;       (* 5a set/get current time of day *)
    swrtprotect    = 91;       (* 5b set drive write-protect vector *)
    sgstate        = 92;       (* 5c Priv., terminal mode, checks *)
    dodelay        = 93;       (* 5d millisecs *)

(* 84-85 remapped onto 92-93 to avoid BYE5 conflicts 86/11/16 *)

    (* subcommands for the master RSX system call *)
    killrsx        = -1;       (* -1 remove system *)
    enquire        = 0;        (* 0  is RSX executing. yes=0ffh no=0 *)
    rsxversion     = 1;        (* 1  of running system *)
    qclkrate       = 2;        (* 2  CPU clock rate in 100khz *)
    qsecure        = 3;        (* 3  state of security flag *)
    resetsecure    = 4;        (* 4  set security off *)
    setsecure      = 5;        (* 5  set security on. *)
    qnoiseflg      = 6;        (* 6  state of noise suppress flag *)
    resetnoise     = 7;        (* 7  turn noise suppression off *)
    setnoise       = 8;        (* 8  turn noise suppression on *)
    screendump     = 9;        (* 9  ONLY if f0k so configured *)
    gdefdrv        = 10;       (* a  get default drive for ENDCALL *)
    gdefusr        = 11;       (* b  get default user *)
    ghomdrv        = 12;       (* c  get home drive, after du error *)
    ghomusr        = 13;       (* d  get home user *)
    grdrv          = 14;       (* e  get receive drive, file xfr *)
    grusr          = 15;       (* f  get receive user *)
    gprdrv         = 16;       (* 10 get private rcv drive *)
    gprusr         = 17;       (* 11 get private rcv user *)
    gpsdrv         = 18;       (* 12 get private send drive *)
    gpsusr         = 19;       (* 13 get private send user *)
    gwrtprotect    = 20;       (* 14 get write-protect vector *)

    (* and subcommand/primitives for modem communications system *)
    initmodem      = 64;       (* 40 enable any subsystems *)
    quitmodem      = 65;       (* 41 disable any subsystem, hang up *)
    stopmodem      = 66;       (* 42 disconnect communications *)
    gomodem        = 67;       (* 43 re-enable communications *)
    breakmodem     = 68;       (* 44 emit a break *)
    answercall     = 69;       (* 45 for non-intelligent modems *)
    qringing       = 70;       (* 46 non-zero means ring detect *)
    dskstop        = 71;       (* 47 anticipatory disk motor stop *)
    dskrun         = 72;       (* 48 anticipatory disk motor on *)
    clearscreen    = 73;       (* 49 clear local (not remote) screen *)
    add1min        = 74;       (* 4a advance time of day *)
    (* END of system commands to RSX subsystem *)

    (* System state bit fields, via sgstate *)
    whlbit         = 128;      (* special priv, implies next two *)
    dunochk        = 64;       (* no access restrictions *)
    devices        = 32;       (* non-sharable device access, eg LST *)
    carcks         = 16;       (* check for carrier on *)
    conoff         = 8;        (* remote console disabled *)
    remon          = 4;        (* remote char. i/o enabled *)
    echol          = 2;        (* local console echoes *)
    echon          = 1;        (* remote console echoes *)