4 ms·

One needs a FXS port, the other needs an FXO port. FXO's are only commonly found on telco gear. https://en.wikipedia.org/wiki/Foreign_exchange_service_(telecom

• gorkish 3y ago
  Err in this case, the modems would both need to connect to "FXO" ports. All they actually need is loop current. The simplest circuit is just a battery, resistor, and capacitor. Fun tip: this also works to directly connect DSL modems.
  • Scoundreller 3y ago
    I thought that only worked for SDSL modems?
    • gorkish 3y ago
      Yes it requires that the DSL mode is compatible. Also on second thought I am 99% sure you don't need a wet loop for naked dsl, but you certainly do for analog modems. Sorry for the misleading info; it has been /a while/ since I hacked on copper PSTN stuff...
      • kjs3 3y ago
        You're right; don't need a wet loop for DSL. We used to back-to-back DSL modems without them all the time. At least for particular brands (which often advertised they could do this)...maybe there were some that didn't support this. I had a guy on the team in those long ago days who figured out how to channel-bond a pile of SHDSL modems over a couple of intra-campus phone cables (much less than CAT3 conformant) to get almost 10base-T speeds over a couple of 100m. In the end, we decided the cost of running a fiber was going to be less than the cost of maintaining the DSL solution, as clever as it was, and gave the upgrade path to whatever we wanted.