The Control & Processing board is now complete and contains the following.
The RS232 input/output circuit is a cmos single rail interface (z5369) which talks directly with the (Motorola 68HC05) I2C bus master control processor.
[http://mot-sps.com/mcu/documentation/pdf/ccvd.pdf]
Philips I2C is the control system selected for the exchange.
I2C is then distributed out/in with 4 available interrupts. Ir1 is allocated to the DTMF decoder
(145436 x 2 - one for each transmission bus) board.
Ir3 is dedicated to the transmission driver control boads (seen on page 7) and Ir4 is dedicated to the uniselector processor (also an 68HC05)
The uniselector processor monitors the HOME position of the uni's, and pulses a 5ms burst of 48v to step them around. (hunting speed is not yet programmed)
This processor keeps track of the positions of all 8 uniselectors and reports back to the PC.
Ir2 has been left for the Subscriber Line interface boards (yet to be designed & built) and also the Subscriber services such as time, temp, remote control, wake up reminders etc......
(145436 x 2 - one for each transmission bus) board. 
Operator....
