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I'm a little too young to have had the pleasure of using modems and serial ports professionally, so I hope someone who has can help me out:
One of my gigs has an old APC PDU, model AP9211. Among its features is a serial console, which you can log into by e.g. HyperTerminal to manage the outlets. They wanted this to be an available out-of-band by a modem, so they can call into and manage in the event of Something Bad happening at their office, which seems like a good idea. However, the guy who set it up has it running through a crappy PC that's actually being used by one of their staff, and (I presume) forwarding the data from the modem attached to the PC to the console of the PDU on another serial port:
-POTS---> Modem ---RS232:COM1---> PC ---Null Modem Cable:RS232:COM2---> PDU Console
I've tested the cable to be a standard null-modem cable, which would indicate to me that the console port on the PDU is a standard DTE serial port. According to the PDU manual, the port is set at 2400baud, 8 data bits, 1 stop bit, no parity, no flow control.
What I'd like to be able to do is hook the modem directly to the PDU, and be able to call directly without the PC. I've got the modem into auto-answer mode, and when its hooked up to a PC and both ports are set to the same speed the PDU needs, it will transmit no problem, so I think its in working order. However, when I hook the modem up to the PDU, nothing comes through: the RD light on the PDU's modem flashes, but there's no response and it never sends anything back to the PC.
So, I guess my question is: should this work? Should I be able to put a modem on both ends of a connection that can be made by null-modem, dial, get a carrier, and be able to send? Or was that just a fluke between two PCs?
Second, if someone is willing to help, what should I be looking for to help figure out what's wrong here?
One of my gigs has an old APC PDU, model AP9211. Among its features is a serial console, which you can log into by e.g. HyperTerminal to manage the outlets. They wanted this to be an available out-of-band by a modem, so they can call into and manage in the event of Something Bad happening at their office, which seems like a good idea. However, the guy who set it up has it running through a crappy PC that's actually being used by one of their staff, and (I presume) forwarding the data from the modem attached to the PC to the console of the PDU on another serial port:
-POTS---> Modem ---RS232:COM1---> PC ---Null Modem Cable:RS232:COM2---> PDU Console
I've tested the cable to be a standard null-modem cable, which would indicate to me that the console port on the PDU is a standard DTE serial port. According to the PDU manual, the port is set at 2400baud, 8 data bits, 1 stop bit, no parity, no flow control.
What I'd like to be able to do is hook the modem directly to the PDU, and be able to call directly without the PC. I've got the modem into auto-answer mode, and when its hooked up to a PC and both ports are set to the same speed the PDU needs, it will transmit no problem, so I think its in working order. However, when I hook the modem up to the PDU, nothing comes through: the RD light on the PDU's modem flashes, but there's no response and it never sends anything back to the PC.
So, I guess my question is: should this work? Should I be able to put a modem on both ends of a connection that can be made by null-modem, dial, get a carrier, and be able to send? Or was that just a fluke between two PCs?
Second, if someone is willing to help, what should I be looking for to help figure out what's wrong here?