On 9/4/2015 11:10 PM, dwight wrote:
  The idea for using the tristate control for an OC
output has been
 used many times before.
 An example is on the SwyftCard for the Apple 2e.
 It needed a OC for the reset as I recall and the PAL used
 that trick.
 The only possible issue is the limited current drive for older
 DTL circuits.
 Dwight
                                           
Exactly - whether you can use the trick depends on what is connected to
that OC output.
JRJ