how did auto trans shift before TCU/with a hydra-matic?

i've been trying to figure out how auto trans shift, and according to Wiki learned that modern cars (since late 1980's) use TCU, the car's computer/Transmission Control Unit. I was wondering how they shifted before computer use and learned that the hydra-matic /hydramatic was the 1st ayto trans ever to be fully auto with no clutch at all. So, I've been googling everything i can think of and can't find an explenation on how the hydramatic actually changes gears, which is a big supprise to not find so many different sites about THE 1ST AUTO TRANS!
The Wiki hydramatic page doesn't say anything about not using a clutch, let alone how it even changes the gears is. It says : "The HydraMatic was designed to combine hydraulic operation of a planetary gearbox (allowing much shifting to be automated) with a fluid coupling instead of a friction clutch, eliminating the need for de-clutching." which indicates that it DOES use a clutch. so A), how can they claim it's fully auto and B), this old advertisement says "there's no clutch" and "all shifting is automatic" http://www.youtube.com/watch?v=zUytf6CFi7U (http://www.youtube.com/watch?v=zUytf6CFi7U)

basically just trying to figure out how the 1st auto trans/ or even non computer based auto trans shifted gears without a clutch and searched for hours with no answer. anyone?

Oh boy, where to begin? One can write a book on this stuff.

First of all, non-computer-controlled fully automatic transmissions have been around for decades, and use the same basic principles, regardless of manufacturer, such as GM, Ford, Chrysler, Borg Warner, Z-F, etc.

Virtually all traditional automatic transmissions do have clutches (or a combination of "bands" and clutches). However, one clutch will engage one gear only, and not the entire transmission, such as a traditional manual transmission. These clutches are controlled automatically, eliminating the need for a manual clutch, hence the advertisement that there is no "clutch".

All these transmissions use a "valve body" which is essentially a very simple mechanical computer. These valve bodies use pressurized fluid instead of electricity.

Based on inputs such as gear selection (Drive, Reverse etc), output shaft speed, throttle position, intake manifold vacuum, the valve body will control and direct the fluid through a series of small passages inside the transmission. This pressurized fluid is used to activate or deactivate specific hydraulic cylinders in coordinated sequence. These cylinders will engage or disengage clutches or bands which then engage or disengage actual gears, allowing the transmission to operate.

All torque converters or fluid couplings used in these transmissions allow for "slip" at low engine RPM. Therefore, at idle, the converter housing spins with the engine, while the output shaft, connected to the transmission does not move. As engine RPM's increase, this gradually becomes an almost solid link connecting the engine and transmission. This operation duplicates the effect of slipping a manual trans clutch until the vehicle is rolling.

The individual clutches or bands controlling each gear are designed to shift under load, so, unlike a manual transmission, the engine does not have to be disconnected from the trans during the shift.

Finally, the first HydraMatic intriduced in 1939 used a "fluid coupling", and four gears. Like a modern automatic, you still had to "shift" it into Drive, or reverse, or Low (for descending steep hills etc) hence "much" but not all shifting is eliminated. Once in gear, its shifting was fully automatic, hence the advertising claim.