I have some outdoor lighting that would stay on dusk to dawn. I also have a photocell controller that would keep a few of them on at a low setting but when some one would enter the walkway they would get brighter. It was made by Edison Lighting. It has stopped working and only stays on low. Anybody know of a replacement for this?

Sounds like the Photocell.
You can use readily available parts, such as Photocell and Motion detector, Just wire the lights like photocell controlled lights, Have the constant hot on the same circuit hot, neutral to neutral, and the switched out of Motion will go to the Lights hot/photocell out.

So your saying add a bypass circuit arount the unit I have that is controlled with a motion detector. This should work if I am unable to find a replacement like I have.

I would say, if unit is defective, replace with a photocell and a motion, if motion still works you may be able to use that, I forgot, you will need a dimmer.
The photocell's out goes in to dimmer, out of dimmer to lights.
The motion will bypass the dimmer and photocell.

The dimmer will have a lot of trouble operating into a transformer unless the right dimmer is chosen.

There has to be much more to this than meets the eye.

A few on low

Wattage of the lamps would help.
Could be series connected lamps, but surprised it isn't all on low.
Transformer taps are another posibility.

Reducing the mains voltage with a transformer is another possibility. You can add/subtract AC voltages or evenuse a 240/120 primary transfomer and use the 240 tap for 50% and 120 tap for 100%. You could even use a 120/240/277/480 for greater control.

A dimmer designed for ceiling fans might work.

Then there is a little logic and some relays to make it happen.

All dim and all brighten when there is motion is relatively easy, but some on low and some off leads me to believe that there may be two wiring sets.

So, it's kind of hard to tell what's going one, but:
1) method to select the string
2) Method to dim
3) Photocell or dusk/dawn timer that uses sunset/sunrize times
4) Motion sensor

If it were a single string that operated as all dim then brigten when someone passes by. The timer or photocell controls power which is switched by relay that either selects dimmed or full power.

If there were two strings then the full power mode would light both strings and only one would use dimming.

Some motion detectors won't respond if it's light outside, so this kills two birds with one stone. The one I have uses a wireless motion detector, but I'm using it indoors. It came with a remote receiver that can be used as a driveway annunciator or turn on a lamp. So this could work with the control circuits inside the house. Just wire the outlet to a relay and switch from full to dimmed power.

I got the motion detector at Lowe's.

Many low voltage halogen lighting systems use similar transformers, any dimmer designed to work with these should work.

Have you tried to contact the manufacturer?

My question is a little misleading. When I said a few I should have said I branched off the main line a few lights. In other words I have 30 lights. 24 are just your normal 12 volt malbu spot and flood type lights. I then have a controller connected ( just like it was another light) to which 6 more lights are connected that are normally half as bright as the 24 but when someone enters the area around the front enterence doorway they go to full bright just as if someone was at the door and saw them comeing and turned the lights brighter.This controller was made by the Edison Company. It came with the 6 lights I have conneced to it but instead of using the transformer that came with it I use a single transformer to controle them all which can be set to work D to D or 2-4-6-8 hours. It's beeen working for the last 12 years and like I said the Edison controller broke and only stays at the low setting. The Edison controller is no longer made but I can't even find anything similar to it. The bottom line is I need a 12vac contoller (transformer) that has a hi low output that can be controlled with a motion sensor.

Diagram attached

I Take it since the Edison Controller has 12 Volts Feeding in, then the bulbs are Low Voltage.
Where is the Motion Sensor(s)? Fixtures, controller, separate?
Confirm all bulbs are low voltage, and
Only 2 conductors between the lights.

Here is a photo of the unit. Yes it is able to control hi/low 12vac with a motion sensor.(Has other features like daylight sensor and timed hi output also. I have it set to stay on for 10 minutes when motion id detected). It is controlling six 12vac surface mounted lights. It is connected in parallel with the other 24- 12vac lights because I am able to control all the lights at one time with a single transformer which also is controlled with a Dusk to Dawn or 2-4-6-8 hour timeer with starts at dusk. Again I am looking for any kind of 12vac control which can always be on with a low (6-8 vac) output but will go to full output (bypass what ever it uses to drop output) when motion is detected. Dose not need off setting.