49.9k as a summing resistor??

[mhartung]

I have been researching summing networks for a while and have come across an early API schematic, but it's not complete. I do however see that all of the bussing out of each input channel uses a 49.9k resistor on both the + and - legs of the busses, including solo busses. Is this the summing resistor to which all channels are connected? I was expecting a much lower value, OR maybe this resistor has a completely differennt function? Anyone have any info?

thanks

Mike