Servo Driver uses 4 x 1.5 AA bateries to power the servo and to send out a signal pulse to control the servo. It replaces the need to use your Tx/Rx
I have built 2 from circuits on the web giving 1 to 2 mS and 0.6 to 2.4mS. There are circuit diagrams, stripboard layout, full costed parts list (with Buy Now links to Rapid Electronics) and build phots.
Tests show them to be accurate.