`The Art of Electronics' (Horowitz & Hill, Cambridge University Press, ISBN 0-521-37095-7) On page 574 is a nice little table that lists what you can drive with what.
TTL | HCT/ACT | HC/AC | 4000B/74C@5v |
+------+---------+-------+--------------+
TTL | OK | OK | A | A |
+------+---------+-------+--------------+
HCT/ACT | OK | OK | OK | OK |
+------+---------+-------+--------------+
HC/AC | OK | OK | OK | OK |
+------+---------+-------+--------------+
4000B/74C | OK * | OK | OK | OK |
@5v | | | | |
+------+---------+-------+--------------+
Need:
Modems - Signal Standards@
See also: