X.21 Kabel - Das muß man wissen
WAN-Verbindungen über X.21 laut CISCO
(mit Hilfe der Synchronous Serial Connection)
Before you connect a device to the synchronous serial port , you will need to know the following:
1. The type of device you are connecting to the synchronous serial interface. - That means : Is the router being connected to a data terminal equipment (DTE) or data communications equipment (DCE) device?
2. The type of connector, male or female, required to connect to the device.
3. The signaling standard required by the device.
DTE oder DCE
A device that communicates over a synchronous serial interface is either a DTE or DCE device.
A DCE device provides a clock signal that paces the communications between the device and the router.
A DTE device does not provide a clock signal. DTE devices usually connect to DCE devices. The documentation that came with the device should indicate whether it is a DTE or DCE device. (Some devices have a jumper to select either mode.)
Das sagt die ITU:
Die ITU ist aus "International Telephone and Telegraph Consultative Committee" (CCITT) hervorgegangen und legt weitgehend weltweit die Standards fest.
[X.21] Recommendation X.21 (09/92) - Interface between
Data Terminal Equipment and
Data Circuit-terminating Equipment
for synchronous operation on public data networks.
Und alle meinen dasselbe !!!! Übrigens soll X.21 und V.35 auch dasselbe sein.
Typical DTE and DCE Devices
- DTE (Data Terminal Equipment) or DCE (Data Communication Equipment)
- CSU/DSU = Channel Service Unit / Data Service Unit
| Device Type | Gender | Typical Devices |
| DTE (hat keine Clock, bekommt Timing) |
männlich | Cisco Router; Terminal, PC |
| DCE (hat die Clock, liefert das Timing) |
weiblich | X.21/G.703 Konverter, CSU/DSU, Multiplexer |
Erläuterungen :
1. wenn Du Pins am Stecker hast, the connector is male=männlich.
2. wenn der connector Löcher hat to accept pins, the connector is female=weiblich.
3. CSU/DSU = Channel Service Unit / Data Service Unit.
X.21 devices, that communicate over a serial interface, are divided into two modes: DTE and DCE. The most important difference between these types of devices is that the DCE device supplies the clock signal that paces the communications on the bus. The documentation that came with the device should indicate whether it is DTE or DCE (some devices have a jumper to select either mode).
Is a male or female connector required on the cable? (noch eine Tabelle)
| Type DTE DCE Selectable DTE or DCE |
| Device |
| Stecker |
DTE-Schnittstelle
(i.d.Regel männlich)
(Empfänger des Clock-Signales)
X.21 / V.11, 15-polige D-Sub Buchse (des Routers)
| Pin Nr. | X.21 / V.11 | Richtung | Funktion |
| 1 | |||
| 2 | Txd(+) | -> | transmit data |
| 3 | Ctrl(+) | -> | control |
| 4 | Rxd(+) | <- | receive data |
| 5 | Ind(+) | <- | indicate |
| 6 | Set(+) | <- | signal element timing |
| 7 | |||
| 8 | GND | <-> | signal ground |
| 9 | Txd(-) | -> | transmit data |
| 10 | Ctrl(-) | -> | control |
| 11 | Rxd(-) | <- | receive data |
| 12 | Ind(-) | <- | indicate |
| 13 | Set(-) | <- | signal element timing |
| 14 | |||
| 15 |
DCE-Schnittstelle
(i.d.Regel weiblich)
(Sender des Clock-Signales)
X.21 / V.11, 15-polige D-Sub Buchse (des X.21 Wandlers =TA)
| Pin Nr. | X.21 / V.11 | Richtung | Funktion |
| 1 | |||
| 2 | Txd(+) | <- | transmit data |
| 3 | Ctrl(+) | <- | control |
| 4 | Rxd(+) | -> | receive data |
| 5 | Ind(+) | -> | indicate |
| 6 | Set(+) | -> | signal element timing |
| 7 | |||
| 8 | GND | <-> | signal ground |
| 9 | Txd(-) | <- | transmit data |
| 10 | Ctrl(-) | <- | control |
| 11 | Rxd(-) | -> | receive data |
| 12 | Ind(-) | -> | indicate |
| 13 | Set(-) | -> | signal element timing |
| 14 |
X.21 für CISCO
(Serielles Synchron Interface an den CISCO Routern)
CISCO X.21 Cable Assembly - Diese Kabel gibts bei CISCO fertig !!!
The cable itself identifies the Cisco router as a DTE or DCE device to other devices in the network. !!!!
An ASCEND router seems to be a DCE allways - why ?? currently no explanation.
X.21 DTE
Cable Pinouts (DB-60 male to DB-15 male=männlich ) Cisco Type CAB-X.21MT
| 60 Pin | Signal | Description | Direction | 15 Pin | Signal |
| J1-48 J1-47 |
GND MODE_2 |
Shorting group | -- | -- | -- |
| J1-51 J1-52 |
GND MODE_DCE |
Shorting group | -- | -- | -- |
| J1-46 | Shield_GND | Single | -- | J2-1 | Shield GND |
| J1-11 J1-12 |
TxD/RxD+ TxD/RxD-- |
Twisted pair no. 3 |
===> ===> |
J2-2 J2-9 |
Transmit+ Transmit-- |
| J1-9 J1-10 |
RTS/CTS+ RTS/CTS-- |
Twisted pair no. 2 |
===> ===> |
J2-3 J2-10 |
Control+ Control-- |
| J1-28 J1-27 |
RxD/TxD+ RxD/TxD-- |
Twisted pair no. 6 |
<=== <=== |
J2-4 J2-11 |
Receive+ Receive-- |
| J1-1 J1-2 |
CTS/RTS+ CTS/RTS-- |
Twisted pair no. 1 |
<=== <=== |
J2-5 J2-12 |
Indication+ Indication-- |
| J1-26 J1-25 |
RxC/TxCE+ RxC/TxCE-- |
Twisted pair no. 5 |
<=== <=== |
J2-6 J2-13 |
Timing+ Timing-- |
| J1-15 Shield |
Control_GND | Twisted pair no. 4 |
-- -- |
J2-8 Shield |
Control GND |
X.21 DCE
Cable Pinouts (DB-60 male to DB-15 female=weiblich ) Cisco Type CAB-X.21FC
| 60 Pin | Signal | Description | Direction | 15 Pin | Signal |
| J1-48 J1-47 |
GND MODE_2 |
Shorting group | -- | -- | -- |
| J1-46 | Shield_GND | Single | -- | J2-1 | Shield GND |
| J1-28 J1-27 |
RxD/TxD+ RxD/TxD-- |
Twisted pair no. 6 |
<=== <=== |
J2-2 J2-9 |
Transmit+ Transmit-- |
| J1-1 J1-2 |
CTS/RTS+ CTS/RTS-- |
Twisted pair no. 1 |
<=== <=== |
J2-3 J2-10 |
Control+ Control-- |
| J1-11 J1-12 |
TxD/RxD+ TxD/RxD-- |
Twisted pair no. 3 |
===> ===> |
J2-4 J2-11 |
Receive+ Receive-- |
| J1-9 J1-10 |
RTS/CTS+ RTS/CTS-- |
Twisted pair no. 2 |
===> ===> |
J2-5 J2-12 |
Indication+ Indication-- |
| J1-24 J1-23 |
TxC/RxC+ TxC/RxC-- |
Twisted pair no. 4 |
===> ===> |
J2-6 J2-13 |
Timing+ Timing-- |
| J1-15 Shield |
Control_GND -- |
Twisted pair no. 5 |
-- -- |
J2-8 Shield |
Control GND -- |