The Clone Theory is one of those larger sheetmetal effect boxes Electro Harmonix produced during the 70s. The Clone Theory was produced around 1977. It is basically a Chorus pedal which can give you Vibrato and Flange sounds as well.

http://files.effectsdatabase.com/gear/pics/eh_clonetheory_001.jpg

The pedal does have three Jack Sockets: One is OUTPUT, there is a DIRECT OUT and the last one is INPUT.
Next to these three Jack Sockets there are three Controls: One for CHORUS/VIBRATO another one for RATE and last control is for DEPTH.

There is also a small toggle switch which gives you the option to change your sound from CHORUS/VIBRATO    to  VIBRATO/FLANGE. The switch acts as a filter to give you variations in sound rather than giving you proper Vibrato and Flange.

All the sounds are very thick and crude even the Chorus which sounds mechanical and robotic, nothing like a Boss CE1.

The pedal is quite noisy, which is the case for most of the older Electro Harmonix pedals. You will not find this a problem when you play.

It seems that Electro Harmonix made a few variations in their effects which could produce Chorus, Vibrato and Flange sounds.
The Electric Mistress does contain some Chorus sounds which are similar to the sounds of the Clone Theory, but the Flange sounds of the Electric Mistress are very different from the one found on the Clone Theory, the Clone does have simpler sounds and gives you less options than the Electric Mistress.

Happy Playing and hope to see you again soon,
Eddie