By clabretro on YouTube:

• Homelab Dial-Up on 2024-05-18.
• Multiple Homelab Dial-up Lines on 2024-06-13.

FX{O,S} voice cards require a PVDM. No PVDM cards in the router? Then FX{O,S} cards won't work.

Cisco 2911 with:

• VIC3-4FXS/DID: for attaching modems:
  • Port 0 has a modem conected, and is configured to dial port 1:

    conf t
    dial-peer voice 10 pots
    destination-pattern 1234
    incoming called-number 1234
    direct-inward-dial
    port 0/1/1

  • Port 1 is connected to line 0 of the first WIC-IAM-V2 in the 2610.
  • Port 2 has a modem conected, and is configured to dial port 3.
  • Port 3 is connected to line 0 of the second WIC-IAM-V2 in the 2610.

Cisco 2610 with:

• 2x WIC-1AM-V2 modem card

By zefie on YouTube:

• First Home v90 (no Telco) dialup video on YouTube on 2021-07-09.
• Home v90 (No Telco) quick overview how on 2021-06-10.
• Dialup V90 at Home - Hardware Info - What I Use [ASMR?] on 2022-10-03.

Setup:

1. Cisco 3825 router as client side with:
   1. T1 controller that can handle data and voice: NM-HDV2-2T1/E1. Can be any T1 on the client side. With the T1 in client mode.
      1. Connected to CSU in server side router with T1 crossover cable.
   2. FXS for the modem connections: WIC-4FXS/DID (WIC-2FXS would also work, DID not needed).
      1. Dials a dial-peer which has the T1 as voice port, to call the digital modems in the 3640.
2. Cisco 3640 router as server side with:
   1. CSU: PRI-2CT1-CSU allows “network-emulation” mode to be the “telephone company”.
      1. Connected to T1 controller in client side router with T1 crossover cable.
   2. Modems: NM-30DM (also known as NM-6DM, NM-12DM, NM-18DM, or NM-24DM, but its all the same card just with more MICA modem modules installed)
   3. An Ethernet card: NM-1E1R
      1. Used to route traffic from the modem to the Internet

The more lines (FXS ports) you want the more PVDMs, the dedicated DSPs that handle voice calls, you need.
An FXS slot requires PVDM.

“In theory you could split up your T1 lines and have 6 of them dedicated to calling the modem and the rest dedicated to a data link.” would bypass the need for a separate Ethernet card(?).