196 vs 185 - phase vs frequency shifting

The Buchla 196 is a phase shifter while the 185 is a frequency /pitch shifter.
Both have pretty similar panels. What's the difference?

The 196 phase shfter.
The manual describes it in the following way:
"It shifts the phase of input signal such that a 90 degrees (+/- 5 degrees) phase relationship between the two outputs is maintained from 5 cps to 20 kc"
Phase shifters can also be found in the Roland 100m (172) & 500m (572) and in the Ken Stone CGS.

A phase shifter uses an "all pass filter", where (I understand) the centre frequency is inside of the audio range. High frequencies are phase shifted either more or less than low frequencies, depending on how the filter is wired.  

The Buchla 185 frequency shifter
The manual describes it in the following way:
"It shifts the frequencies of an input signal by an amount determined by another applied carrier signal.
The shifting is applied to all input frequencies, uniformly.
It is not a transposing device. Rather, it is used to obtain new timbres... usually containing non-harmonic partials."

The front panel of the 185 has two inputs and 4 outputs
The left input is for the main signal, and the right is for the carrier frequency.
The Sum outputs is where the frequencies of the carrier and input signals are added.
The Difference output is where they are subtracted.
If the sum & difference outputs are mixed, you get ring modulation.

It seems that the 185 is actually made out of two 196s, and one dual 111 ring-modulator & a mixer (probably a 106).
A frequency shifter is basically two ring modulators where the original signal is canceled out in the end. So you just get the new side bands, which then get separated.  

The buchla 200 system introduced the 285, 285e & the 297

It's fascinating to the the evolution of the frequency shifter over the years.The 200 series "un-hid" the ring modulator section.

A modern Buchla version of the Phase Shifter is the 297. Called the infinite Phase Shifter 
it can displace the phase of an applied signal by up to 1,800 degrees.

Frequency shifters were also made by Bode & Moog.
The Haible FS-1a is also an excellent frequency shifter