`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:

• CMOS to TTL to etc... interfacing incl: voltage, current (typical sink, source), static, etc..
• EMF interference

Modems - Signal Standards@

See also:

• Resistor color code calc