Bleep generator: adjust trimmers to taste.


                         +5v
                          |
                          |
                          |
                +---------+---------------------+
                |         |                     |
            +---+---------+----+              +-+-+
            |   4         8    |      30K ohm |   |         |
            |                  |              |   |       +-+-+
            |       NE555      |              +-+-+       |   |
   +--------+ 3                |                |         |   |
   |        |                7 +----------------+-------->|   |
   |        |                  |                          +-+-+  20K trimmer
   |        |  1          2  6 +---+------------------------+  
   |        +--+----------+----+   |                        |
   |           |          |        |            .001 uf  -------
   |         -----        +--------+                     -------
   |          ---                                           |
   |           -                                          -----
   |                                                       --- 
   |       +------------------------------------------+     -
   |       |                 74163       Carry out 15 +--------+---------+
   +-------+ 2 Clock                                  |        |         |
           |             Inputs                ----   |     -------      |
           |     A      B      C      D        Load   |     | 7404|      |
           |     3      4      5      6          9    i      |   |       |
           +-----+------+------+------+----------+----+       | |        |
                 |      |      |      |          |             O         |
                 |      |      |    -----        |             |         |
                 |      |      |     ---         +-------------+         |
                 |      |      |      -                                  |
           +-----+------+------+----------------------+                  |
           |    13     12     11                      |                  |
           |    QB     QC     QD                      |                  |
           |        Outputs                           |                  |
   +-------+ 2 Clock         74163                    |                  |
   |       +------------------------------------------+                  |
   |                                                                     |
   |       +------------------------------------------+                  |
   |       |                                          |                  |
   +-------+ 15 Carry out    74163            Clock 2 +------------------+
           |                              QA          |
           |                              14          |
           +-------------------------------+----------+
                                           |
                                         +-+-+
                                         |   |
                            1K trimmer   |   |<----------  Output
                                         |   |
                                         +-+-+
                                           |
                                         -----
                                          ---
                                           -