The KRONE Splitting Butt-Set Adapter is made to be used on KRONE Disconnect Blocks, used for an RJ-21X (primarily in Nynex / Verizon areas).
KRONE Disconnect Blocks are specially made so that when you insert this adapter, it disconnects the CPE equipment automatically - which is like opening the Bridging Clips on a 66 Block.
No other Adapter should be used on the KRONE Disconnect Blocks, since it will NOT open the pair to the equipment, which could cause you to think the phone line is bad when it isn't.
The KRONE Splitting Butt-Set Adapter has four Banana plugs. You simply clip your Butt-Set on the appropriate pair to look OUT (towards the CO), or IN (towards the CPE).
The telephone line is automatically reconnected to the CPE as soon as the adapter plug is removed.