Digital Intercoms

We want Digital Intercoms to be designed, which allows us to use Speech at 8KHz Bandwidth and control data. The intercom system can be interconnected using a RS485 Link or any other digital format which allows upto 1KM. Intercom system will have one master and upto 64 outstations. When the channel is opened, it should allow 2 way speech (Handsfree) between any of the two outstations and the facility to allow additional outstations for a conference intercom. It should also allow the facility to make a PA (Public Announcement) to all the outstation from the Master Unit. We will require an indication of chipsets you will be proposing, circuit diagrams and codes. The project will be in the following phases/milestones for payment:- 1) Proposal - This includes block diagram of the system & chipset 2) Full circuit Diagram 3) Making of two hardware prototypes; one of them to be sent to us for various testing during the software coding. i.e. by sending us relevant software hex files. 4) Final handover of PCB artworks and Code which we can modify if requires in the future. The final payment will be made once we compile the code sent to us and load on the prototype. We will welcome any suggestions and are willing to negotiate depending upon offer and knowledge.