The circuit of the 2 channel DMX repeater is as simple as it can get. Three 75176 Ics translate the signal levels from RS-485 to TTL and vice versa. The input is a typical reciever configuration of the chip. Note the 120 ohm resistor across the inputs.
The TTL output at pin 1 drives the other two 75176 chips which are in a transmitter configuration and provide two full DMX outputs capable of driving the full complement of 32 unit loads. If the reader wishes to increase the number of outputs it would be advisable to insert a TTL line driver between the reciever and transmitters. The reciever, by itself, can drive 2 unit loads safly. A 74HC17 would be a good choice. You can also insert an isolation stage using any high speed optoisolator suitable for above 250KHz operation. e.g. 6N137 (check later for further cicuits in this page, using optoisolation.)
A simple powers upply using a 7805 is also shown running of a +10vDC unregulated line.