This library contains the source code to ZDB V. 1.8.  Released
1/30/92 by Joe Mortensen.
This is revision 1.8B, dated 02/04/92, by Al Hawley. It includes
the following changes from V 1.8:
  a) A "JR CLKOK" instruction is added in the clkok: routine after
the call to fnamz to enable recognition of the default data file.
  b) The modem is reinitialized (in ZDB18.B) with ATZ after the
dialing sequence is finished, resetting register S7 (and other
settings used to dial) to the default. This is necessary for my
version of MEX, which on subsequent invokation does not issue the
ATZ or reset the S7 register. This also guarantees that the modem
will not be left in an unknown state connected to the phone line.