P1 on this Radio Shack circuit is a 6 V lamp with current up to 500 mA depending on Q2. The frequency is given by C1 which can have a modern standard value such as 3.3 uF or even 4.7 uF.
This stage of audio power is suggested by the Hitachi Semiconductor Manual, using a complementary pair at...
This stage is intended to receive modulated optical signals, using as a receiver a photodiode....
This circuit has an automatic dynamic gain control in a range of 6 dB to 40 dB. We found it in...