I understand that you are trying to set up your TMCC operation in the least expensive, yet effective manner. After all, if you have the power source (the old ZW), why not make the most of it. The answer is, you can. My layout of 496 square feet is powered by three PW ZWs with five of six throttles in operation, each connected to a first generation Powermaster and thence to the Command Base. I run TMCC and conventional engines on each of the five loops, simultaneously, often two lines in conventional mode and the other three in TMCC. Just slip the TMCC/Conv slide switch on the Powermaster to your preference for operation. Occasionally, I even run locos in transitional command (combine conventional and TMCC) on the same line. That can be a blast, but is a story for another day. Read all about it in the original expanded TMCC Operators Guide, printed in the early days of TMCC.The layout has been in place since 1996. In fact, before TMCC was on the market, Powermasters came out a bit earlier and I was able to operate all of my engines, some seventy years old, from the just introduced CAB 1. That alone sold me on the whole TMCC concept. But, in response to your questions, you have been given some very good advice. First, assuming your equipment is in tip-top shape, i.e. cords and throttle controls, it is essential that you install quick blow or low amperage in-line fuses on each of your lines, whether you have just one or multiple ones, using Powermasters, whether the older versions or the new 1L (blue box version). The breakers in the PW ZWs are too slow and you will "fry" your electronics in your TMCC locos. As has been pointed out, fuses are cheap, circuit boards are not. If all is well, the CAB1, CB/Powermaster arrangement will operate just fine. Your transformer will be able to handle the set up well, if wiring is adequate and connections are solid. As suggested, assuming you wish to run TMCC and conventional locos, and you must purchase Powermaster (s), the extra cost of the 1L version is well worth it. There are still plenty of the older units on shop shelves and at meets. But, the operative word is older and remember they are no longer made. Just chalk up the price differential between the old and the new as good insurance. If all you really need is 1L Powermaster and some in-line fuses, you are looking at an outlay well south of $100.00.