This PIC microcontroller based RC driver is able to control 4 RC Servo by on board
32 Channel Servo Motor Control Board + PS2 Controller + Receiver
PhidgetAdvancedServo 1-Motor - 1066_1B - Phidgets
6CH Servo Controller Driver Board w/ Bluetooth 4.0 for RC Robot Arm Support PS2 20% Off - AliExpress
20-Channel Serial Servo Controller
4 Channel RC Servo Controller Board
Kitronik Simple Servos Starter Pack for BBC micro:bit – Kitronik Ltd
The Pololu 4-Channel RC Servo Multiplexer can be used with standard hobby radio control systems and servo controller to allow easy switching of servo
4-Channel RC Servo Multiplexer
Servo PCB Controller Board Module For ASMC-04A ASMC-04B High Torque Robot Servos
RC Servo Controllers