AB SLC5/04 Channel 0 Passthrough

I have four SLC5/04s connected over DH+. The OEM remotely supported the four PLCs by modem connection to channel 0 on the PLC with ID 1 (others are 3, 5, and 7). I can connect to channel 0 on any of the four PLCs, but I only see the PLC with ID=1. I'm using the DF1 driver in RSLinx. From the channel configuration in the program file backup I can see that Channel 0 is set up for DF1 Full Duplex with modem handshaking. The port autoconfigures in RSLinx; I just can't see PLC IDs 3,5, and 7. Anybody know a solution?

mfoxips