Teeco still manufactures the old Sargent Sowell design. The controller is a 6 circuit die cam mechanical controller installed in the head. It's timing is preset and not very flexible or upgradable. Teeco offered a pole mount solid state unit, that was slightly more flexible (change times only) but not upgradable or able to support the simplest of detectors. Teeco's stuff didn't meet any traffic signal design standards and isn't used much.