The DS1206N-RS and "-TM" devices have "12V"-to-3.3V switching regulator onboard. Conventionally, the power is supplied through the power jack. The Power Jack of the DS1206N accepts "small" power connectors with 3.5mm diameter. Use APR-P0011, APR-P0012, or APR-P0013 power adapter supplied by Tibbo or similar adapter with 12V nominal output voltage. Adapter current rating should be at least 500mA. On the power jack, the ground is "on the outside", as shown on the figure below.
Alternatively, the DS1206N-RS can be powered through pin 9 of the DB9M (RS232) connector, while the DS1206N-TM can be powered through pin 2 of the TTL interface connector. Two internal diodes combine power jack and pin 9 (pin 2) inputs into a single line, which goes to the internal regulator of the DS1206N.
On the DS1206N-RS, pin 9 of the DB9M connector can also be used to provide "12V" power to an attached serial device. "12V" actually means "input power on the power jack", which is not necessarily stabilized. The power line of the jack passes through a software-controlled switch and is then connected to pin 9 through a Schottky diode (shown on the diagram below). Therefore, the voltage on pin 9 is close to the input voltage on the power jack.
Tibbo serial-over-IP application supplied with the DS1206N has a dedicated "PS" ("Power on pin 9") setting to control the power switch. To turn the power switch on from within your Tibbo BASIC/C application, enable (configure as output) line PL_IO_NUM8_PWROUT and then set this line to HIGH. Additional programming information can be found in TIDE, TiOS, Tibbo BASIC, and Tibbo C Manual (see i.o object and DS1206 platform documentation).
If you want to use pin 9 to power an attached serial device, then you must power the DS1206N-RS itself through the power jack. We know you understand this, but we still had to mention it.
The DS1206N-TS board does not have "12V"-to-3.3V regulator at all. 3.3V power required for board operation must be supplied by the external device through pin 1 of the TTL interface connector.
The DS1206N-TM and "-TS" boards do not have the power switch.