The connectors for both the sending unit and power cord are now equipped with locking rings and mate to the appropriate connectors on the back of the 850. The power cord has 4 pins while the sending unit connector has 3. Rotate the body of the plug until it seats in the connector on the back panel, then thread on the locking ring to lock plug in place.
The fuse holder is now located on the back panel and not in the power cord's lead.
Both the main rotary switch and the auxiliary rotary switch have had "stops" added to them to prevent accidental switching to an unwanted position. To turn the 850 on, the main rotary switch must be turned CLOCKWISE thru TEST. A stop has been placed between Power off and REV.
Zeron 850's can now run in either hundredths of a minute or seconds. A small slide switch located next to the right of the auxiliary display selects the time base. To gain access to the switch, remove the four corner screws and pull the 850 from its case. The switch can be seen by looking between the front panel and the printed circuit board mounted behind it. A pencil can be used to slide the selector to the desired mode. Push the selector to the bottom for hundredths, to the top for seconds. Your 850 comes preset to the hundredths mode.