The Cisco VG244 (voice gateway) was announced EoL in 2014, but the documentation is still available through the Wayback Machine.

It provides 24 FXS ports, exposed over a RJ21 connector on the back side. The pinout is as follows: https://www.cisco.com/c/en/us/td/docs/routers/access/vg224/hardware/installation/guide/hig/higcabl.html

In essence, the pin of the top is the ring and the bottom is the tip, 1 to 24 from left to right. The rightermost top/botton pair is not connected.

Different names are used for an RJ21 connector. It is also used in SCSI cables. From my own experience, I can recommend against disassembling an old SCSI cable because not all pins are connected to a wire, so you can't cut the cable and solder the wires. The second reasons is the high amound of glue used within the connector part, which is a lot of work to cleanup.

But it can be cheaper to buy a '50 pin SCSI connector' on Mouser for example than to try looking for an 'telco' or 'Amphenol connector', which are the names usually used in the telco sphere.

For the patch panel, a very useful thing to know is that RJ11 cables do fit in a RJ45 socket. This is not good for the durability of the patch panel as a RJ45 panel, but if you just continue using it for RJ11, you are fine. Ethernet cables can be used for link agregation. Phone lines are a single pair, Ethernet uses 4 pairs, so they can carry 4 phone lines.

In an RJ45 socket, the middle pair consists of a blue and white/blue cable. That is the pair that is connected with RJ11. On the back side of the patch panel, the order of colors could be changed. Make sure to verify it with a multimeter.

A thing to consider: the patch panel might be 1-indexed, but the Cisco config is 0-indexed.

Full PDF is available here: https://web.archive.org/web/20040708065028if_/http://www.cisco.com:80/univercd/cc/td/doc/product/access/vg/vg224/scg/vg224scg.pdf

Images: http://cios.dhitechnical.com/VG_2XX/vg224/ The VG224 has a CompactFlash slot, but it is known that it does not work well with large cards in the order of gigabites. They come with a Cisco branded CF card by default, but if that is unavailable use a small card of 128MiB or something like that.

https://web.archive.org/web/20180305040316/http://robertmartinwhite.blogspot.com/2017/09/using-cisco-vg224-analog-voice-gateway.html

https://www.cisco.com/c/en/us/td/docs/routers/access/vg224/hardware/installation/guide/hig/higovw.html

https://web.archive.org/web/20040502195202/http://www.cisco.com/univercd/cc/td/doc/product/access/vg/vg224/scg/index.htm

https://gist.github.com/anounyym1/63450d64d4ccf817c4829260101c3b04#file-vg204-conf-L118

Config register

Check before rebooting!
To save the config before rebooting, run `copy running-config startup-config`. Sometimes the config register setting prevent this from working, change it to `0x2102` to make it save configs: 
en
conf t
    config-register 0x2102

Configuration

notes at the RevSpace config: port 1 -> thomastheo phone port 2 -> modem pbx laptop

these are labeled different from config and patch panel:

port 14 -> modem 2 port 15 -> modem 1

note 0-indexing vs 1-indexing

The following is the config at 37C3, but is shown as an example:

!
hostname susco
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
!
!
!
!
voice-card 0
!
!
!         
voice service voip 
 modem passthrough nse codec g711ulaw
!
!
!
!
!
!
!
!
!
!
!
!
archive
 log config
  hidekeys
!
!
!
!
interface FastEthernet0/0
 ip address dhcp
 duplex full
 speed auto
!
interface FastEthernet0/1
 ip address 10.33.33.32 255.255.255.0
 duplex auto
 speed auto
!
interface Dialer0
 no ip address
!
!
ip http server
!
!
!
control-plane
!
!
!
voice-port 2/0
!
voice-port 2/1
 no echo-cancel enable
 no comfort-noise
!
voice-port 2/2
!
voice-port 2/3
!
voice-port 2/4
!
voice-port 2/5
!
voice-port 2/6
!
voice-port 2/7
!
voice-port 2/8
!
voice-port 2/9
!
voice-port 2/10
!
voice-port 2/11
!
voice-port 2/12
!
voice-port 2/13
 no echo-cancel enable
 no comfort-noise
!
voice-port 2/14
 no echo-cancel enable
 no comfort-noise
!
voice-port 2/15
!
voice-port 2/16
!
voice-port 2/17
!
voice-port 2/18
!
voice-port 2/19
!
voice-port 2/20
!
voice-port 2/21
!         
voice-port 2/22
!
voice-port 2/23
!
!
!
!
!
dial-peer voice 101 voip
 destination-pattern .T
 modem passthrough nse codec g711ulaw
 session protocol sipv2
 session target sip-server
 incoming called-number 200*
 dtmf-relay rtp-nte
 codec g711ulaw
!
dial-peer voice 1 pots
 destination-pattern 2001
 port 2/0
 authentication username 2001 password 091E1E5948
!
dial-peer voice 2 pots
 destination-pattern 2002
 port 2/1
 authentication username 2002 password 1357474259
!
dial-peer voice 13 pots
 destination-pattern 2013
 port 2/13
 authentication username 2013 password 1445425A5F
!
dial-peer voice 14 pots
 destination-pattern 2014
 port 2/14
 authentication username 2014 password 135747435F
!
dial-peer voice 102 voip
 session protocol sipv2
 session target sip-server
!
!
sip-ua 
 registrar ipv4:10.42.160.12 expires 3600
 sip-server ipv4:10.42.160.12
!         
!
line con 0
line aux 0
line vty 0 4
!
end