Cisco multi-port voice gateways have one or more ports for analog phones which is called RJ-21. Since the distance between the Cisco voice gateway and the phone distribution frame can be variable, you may need to make a special cable to connect these ports.
You can see the RJ-21 port and pin order used in Cisco multi-port analog voice gateways in the following image:
In the table below, you can find the pin sequence of RJ-21 ports used in Cisco multi-port analog voice gateways:
| Port Number | Connector Pin | Signal |
| 1 | 1 26 |
Ring Tip |
| 2 | 2 27 |
Ring Tip |
| 3 | 3 28 |
Ring Tip |
| 4 | 4 29 |
Ring Tip |
| 5 | 5 30 |
Ring Tip |
| 6 | 6 31 |
Ring Tip |
| 7 | 7 32 |
Ring Tip |
| 8 | 8 33 |
Ring Tip |
| 9 | 9 34 |
Ring Tip |
| 10 | 10 35 |
Ring Tip |
| 11 | 11 36 |
Ring Tip |
| 12 | 12 37 |
Ring Tip |
| 13 | 13 38 |
Ring Tip |
| 14 | 14 39 |
Ring Tip |
| 15 | 15 40 |
Ring Tip |
| 16 | 16 41 |
Ring Tip |
| 17 | 17 42 |
Ring Tip |
| 18 | 18 43 |
Ring Tip |
| 19 | 19 44 |
Ring Tip |
| 20 | 20 45 |
Ring Tip |
| 21 | 21 46 |
Ring Tip |
| 22 | 22 47 |
Ring Tip |
| 23 | 23 48 |
Ring Tip |
| 24 | 24 49 |
Ring Tip |
| – | 25,50,51,52 | GND |