PCMxA
PCMxA is a generic term for the transmission systems used by Deutsche Telekom for the access network . The systems serve the multiple use of copper connection lines for analog telephone connections . They always consist of an exchange-end device ( PCMx V A ) and a subscriber-side device ( PCMx T A ).
The "x" is a placeholder for the maximum number of connections that the system can multiplex and transmit via pulse code modulation (PCM).
In addition to this, there is also a number that identifies the device generation. The devices of the second generation (e.g. PCM2VA 2 ) used until around the year 2000 had to be exchanged for devices of the third generation (e.g. PCM2VA 3 ) with analog connections with a performance feature for call number display (CLIP) , since the second generation does not have a CLIP supported.
PCM multiplexers are mainly used when there are no longer enough free twin wires in the access network (for example between KVz and APL ) to implement a telephone connection.
Overview of the systems
PCM2
- Multiplexer for two analog telephone connections via a twin wire
- 2 × 64 kbit / s user channels + 16 kbit / s control channel
- Coding: 2B1Q or 4B3T
- A modified form of the ISDN transmission technology is used for transmission.
PCM4
- Multiplexer for four analog telephone connections via a twin wire
- 4 × 32 kbit / s user channels + 16 kbit / s control channel
- Coding: 2B1Q or 4B3T
- A modified form of the ISDN transmission technology is used for transmission
PCM11
- Multiplexer for 11 analog telephone connections via a twin wire
- 11 × 64 kbit / s voice channels + 80 kbit / s control and synchronization channel
- Coding: 2B1Q
- High Data Rate Digital Subscriber Line (HDSL) is used as the transmission technology.
properties
- The subscriber-side devices are usually of the switch with a voltage from 110 to 160 volts DC and 320 volt DC (PCM11) remotely powered .
- Instead of the usual 60 volts, there is only a voltage of around 40 volts at the subscriber interfaces.
- With connections that are switched via a PCM multiplexer, analog modems only achieve a data transfer rate of around 33.6 kbit / s.
- With connections that are switched via a PCM multiplexer, it is not possible to provide a DSL connection, as the connection does not have a dedicated continuous copper pair.