This circuit is from the 80's but uses common components today. The relay is voltage sensitive according to the power supply used. Transistors may be general purpose types.
This amplifier has a few Watt output, using old transistors. The speaker is 45 ohms, but with...
This circuit was found in an 80's Electronic Design. It amplifies TTL fast signals for a coaxial...
This circuit uses a Norton operational amplifier to generate 1 kHz pulses with a 1 to 60...