The Mains 100-250V AC electronic On/Off switch, controlled by a low-volt signal

I order to be able to automatically turn on and off the mini transformers of peripherals to my computer, I have dug out this electronics project from the late nineteen eighties for this pc mod.

It is a triac operated 220V AC switch, capable of 2 Amp without extra heat fins, and as much as
6.3 Amps with a small heat fin. It will actually operate as low as 24V AC and as high as 400V AC, but still within the same Amp range.

It is controlled by a small opto coupler MOC3041.

An opto coupler has the advantage that the control signal is carried by light, thus absolutely electrically separating the low-voltage side and the high-voltage side of the circuitry.
One should always maintain a minimum distance of 6 mm between the low-voltage copper/solder point and the high-voltage copper/solder points.

On the low-voltage side is only a LED. In this chip it starts reacting at 3mA current which is reached at about 2.2V. So with a 5V or 12V power source you need a small resistor to lower the voltage to the right level, and you are set on the control side.

The MOC3041 also has the advantage of a zero-detection circuitry on the high-voltage side, ensuring an absolutely smooth ON switch of the high current side.

To get the two drawings to fit, you have to remember that the "pcb side" drawing will be mirrored when it is put on the copper side of the pcb.

A word or two about the AC connectors
If you have an exciting setup, and cut one AC wire to insert this board, then use AC1 and AC4. 
Otherwise the AC1+2 are AC IN and the AC 3+4 are AC LOAD

Component list
R2  330 ohm - orange orange brown
R3   56 ohm  - green blue black
R1   39 ohm  - orange white black
C1  0.01 uF / 630V
BT138 triac
Fuse - 2A to 6.3A depending on heat fin size

R4  470 ohm - yellow purple brown
MOC3041 opto coupler chip