Black Box Async RS-232<->RS-485 Interface Converter - serial adapter - RS-2

The IC1476A-F converts unbalanced, full-duplex RS-232 signals to balanced half- or full-duplex RS-485 signals. It uses two user-selectable methods to enable the RS-485 driver, either by toggling Request to Send (Pin 4) of the RS-232 side or by automatic sensing of the data on the Transmit Data (Pin 2) of the RS-232 side. By removing both sets of jumpers, you can constantly enable the RS-485 driver and receiver. In other words, it can act like an RS-422 converter, unlike the other converters here, which use data to control the RS-485 transmitter.