Question:  What dip switch or jumper plug settings are available on the CS-702 portable main station that require removal of the dust cover?
Answer:  To access the internal options and adjustments, you must remove the station’s cover to gain access to the internal circuit board.
NOTE:  Before removing the station’s cover ensure the power to the station is disconnected from the AC mains source!
Remove the screws on either side of the station. Remove the four screws on the top of the station. Remove the cover.
NOTE: These adjustments should only be carried out by qualified service personnel.
1 JP-1 and JP-2 Line Length Selection Jumpers: Jumpers JP-1 and JP-2 allow the optimization of the hybrid null circuitry for excessive intercom cable lengths. JP-1 is for channel A and JP-2 is for channel B. 
Each jumper has three pins, labeled L, S, and M. A jumper plug is placed over pins L and S, which is the default position for the pins. Moving the jumper plug to place it over the following pin sets reconfigures the station for the following line lengths:
• Long Lines. For line lengths in excess of 500 feet (152.5 m), place the jumper plug over pins L and S. This is the default position to which the unit is set when shipped from the factory.
• Medium Lines. For line lengths between 200 feet and 500 feet (61m – 152.2 m), place the jumper plug over pins S and M.
• Short Lines. For line lengths less than 200 feet (61 m), remove the jumper plug, or store it on the jumper by placing it sideways over pin S.
2 JP-3 Interrupt Enable/Disable Jumper: Jumper JP-3 allows you to select to either mute or not mute active talks when you use the stage announce feature.  The jumper has three pins. When shipped from the factory a jumper plug covers pins 2 and 3 (ON). When the jumper plug is placed over pins 2 and 3, active talks are muted when you use the stage announce feature.  Placing the jumper plug over pins 1 and 2 turns off the muting feature, so that active talks can be heard even when the stage announce feature is used.
3 Headset Audio Limiter: To protect the hearing of the user, the headset audio limiter restricts the maximum audio level heard in the headset. By default, this feature is on when the station is shipped from the factory. You can turn this feature on or off using an internal three-pin jumper.
a. Locate the three-pin jumper labeled “JP4” on the circuit board.  A jumper plug connects pins 2 and 3 of the jumper. This is the on position for the headset audio limiter feature.
b. Lift the jumper plug off pins 2 and 3 and place it over pins 1 and 2. This is the off position for the headset audio limiter.
http://www.clearcom.com/product/partyline/main-stations/cs-702