Just the one adjustment on a Hitec ESC. Used to set the center to match the transmitter.
Electronise ESCs had two adjustments, one for center and another that tweaked the deadband, and, coincidentally, the end points and the rate of speed change.
Same problems on both, users more used to hammers and chisels and muscles rather than small screwdrivers and finger and thumb adjustments and an iability to read the labels saying which wires were for power supply, and which were for connection to the motor.
Hitec designed theirs around the idea of a Hitec based system, Electronise's Electonic Speed Control had to work with anybodys transmitter.
I have no doubt that, having survived this long in good condition, they should continue giving good service.
The old ESCs, because of the way they worked, gave a low, rumbling growl from the motor. Modern ESCs tend to cause the motor to whine, one of the prices of progress.