This is a high frequency astable multivibrator . The diodes are used to keep the frequency the same regardless of changing the duty cycle, which is controlled with the pot. The combination of the pot and diodes allows for a high output of less then 50% to boot!
As a side note the frequency can be adjusted by switching out the main cap and pot with different values, lower values quicker, higher values, slower. Safety resistors of 10 ohm are there to prevent a full short when adjusting the pot all the way up.
