Upgrade and loader program are both free on MTH's protosound website. You need to download both. The 4.3 upgrade program is a zip filed that unloads into 2 files, one with the suffix .rem and the other .tiu
When you run the program, it gives you step-by-step instructions. You run the program before connecting anything, and thereafter it gives you instructions as you reach the various steps.
You will need:
1. a stereo cable with 1/8" jacks at each end, about a foot long.
2. a power supply to feed the TIU through the AUX port.
3. a telephone handset (not wall-to-set) cable to connect TIU and remote.
4. A cable to connect computer and TIU:
a. If a TIU prior to Rev L and
(1) your computer has a serial port, a regular serial connector cable, or appropriate gender;
(2) your computer has no serial port, a USB to serial cable. Radio Shack has one by Gigaware that I use.
b. If a Rev L TIU, an appropriate USB cable.