+1 Lone Haranguer except I would say the long DA pull is not a
safety per se, but like a DA revolver it makes the trigger pull
a deliberate conscious act whereas with SA, with adrenelin
etc. a premature discharge could occur.
For the O.P. you refer to a 'Lock" ?? Perhaps you mean
a manual safety w/lever that manipulates the mode?
FYI some DA/SA handguns have a manual safety however how
and when it is capable of operation depends on the platform
design. Example, the CZ 75B standard has a frame
mounted thumb safety. It is only operational if the
hammer is at full cock, i.e. Single Action Mode. It does not
have a decocker so the hammer must be carefully lowered
manually to revert to DA mode. Now that is not to say
that that is true for all copies of this or variants of tthe
design You're doing the right thing asking in order to figure
out a platforms Manual of Arms/operations
Randall