NAL's SYN-DC-936 converter allows one to powera a A3LA modem using a 12V (car) battery.

NAL's datasheet shows modem-end connector attached to a modem. Unfortunately the connector encloses the clamp-down screws so a small phillips screwdriver is required to open the connector and screw the unit into the modem to form a reliable attachment.

The datasheet does not show the standard DB9 connector that plugs into the controller. Adjacent to the DB9 connector, coming out of the shrink-tube-ended cable, are the plus (red) and minus (black) power leads, each about three inches long and tinned at the ends.