Hello all. I am looking for a phototach that is CSI or is compatible with the CSI so that we can have as a backup in case of emergencies.

Monarch SPS-5/115, ROS-5P Optical Sensor, Interface Module, and 115 Vac recharger/power supply kit will work with your 2115:
http://www.reliabilitydirect.com/tachometerproducts/tachsensorproducts.htm

Thanks Dave, I will check it out. We have three 404's to use with our 2120's, but I have to train one of the motor shop techs how to balance if the need arises. We have the 2115 with Fastbal but no other 404. If the cost of the Monarch is better and will make it work...