RS-485 is a single duplex, differential, multi-drop capable serial communications method. This module has TTL level I/O pin header including 5V, RX, TX, read enable, transmit enable, and ground. Wiring was done above board for self documenting. LEDs are included for the TTL lines. Jumpers are provided to connect a 180 ohm RS-485 termination resistor, source or receive 5V to the RS-485 socket, and whether to tie the read and transmit enable lines together. The RS-485 socket accepts a screw terminal connector (not shown). The voltage regulator is included for translating incoming voltage (7V-20V) to 5V. This circuit is built around the Linear Technology RS485 transceiver LT1785.