From what you have described it looks like traffic is going to go only one way ..
It also doesn't look like you need any way of acknowledgement of the received data ..
So, you don't need full master-slave protocol, but rather one-transmitter-to-16-receivers configuration ..
Of course you can use differential bus (even MAX485 transceivers) which is noise-immune and allows you to connect all 17 devices together, but as far as software is concerned a string with stage of switches and a check-sum sent every certain period of time (one way) should be sufficient ..
As far as hardware is concerned, I'd strongly advocate the use of PICAXE family, perhaps PICAXE-28 as transmitter and PICAXE-08 as receivers, all equipped with MAX-485 (or equivalent) differential bus transceiver ..
Rgds,
IanP
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