The Adapter is a junction box to expand the 25-pin connector on the Controller to multiple signal sources.
It also contains the RF receiver and some signal conditioning. It includes these:
1. The pigtail from the Controller′s 25-pin connector is wired to an Interconnect Board. This contains the following:
  * Resistors to common for most analog inputs because their sources are op-amps which are not rail-to-rail.
  * A circuit for the line monitoring function which converts a wide range of AC and DC inputs to an acceptable logic input to the processor in the Controller.
  * A triple filter and 4:1 attenuator for the Auxiliary DC measuring input.
  * Headers for each input source, plus a spare.
2. A pigtail with a 5.5 x 2.1 plug providing 4.7 V to the Driveway Patrol Receiver. It is connected to a circuit board which not only contains the regulator but also detects the current surge when it sounds an alarm. This produces an open-collector logic output. Since this device sounds 3 beeps, multiple event messages result.
3. The RF receiver is another circuit board. Its design is similar to the Flower Receiver, but adds a comparator to buffer the high-impedance interrupt output.
Here are photographs

Here are the circuit diagrams