Kelly is a RS232 and CSAFE development board. The board can be configured as either RS2323 or CSAFE by populating its respective components. Do not supply power to the DC Jack while using CSAFE, which supplies the board power too. This is safeguarded with solder pads that must be bridged in order to power the board.
RS232 is implemented with flow control (RTS/CTS).
Wikipedia has a helpful article on CSAFE.
As mentioned above there are two options for powering this board. When using the DB9/RS232 variant power is supplied via the DC input jack (5V DC).
The CSAFE variant draws power via pin 5 on the RJ45 connector.
Two headers are available to connect 3V3, VIN and GND to other devices.
The DB9 connector is wired as male and has the following pinout:
CSAFE connector pinout (from the perspective of the development board):
Revision-controlled example firmware for the Kelly board is available on the Electric Imp GitHub examples page.