Originally the E1 frame was developed to connect PABX systems carrying 30 PCM encoded voice channels together with associated signalling. The PCM digitisation rate is 8000 samples/second x 8 bits/sample, or 64Kbps. The signalling for all 30 channels takes a further 64Kbps. The aggregate of 31 channels represents a data rate of 64Kbps x 31 or 1984Kbps. Because the E1 framing rate is also 64Kbps, the operating rate of the E1 carrier is 2.048Mbps.

The E1 frame consists of 32 timeslots, each one byte long. Synchronisation is achieved using the framing information in timeslot 0. The other 31 timeslots are available for use, each giving an effective data rate of 64Kbps.

Using a E1 multiplexer companies can integrate the transmission of voice, data and video between locations, routing this mixture of data onto a common E1 transmission line.

Yes ! An Echo can have four Nx64 channels fitted, but additional Echos may be daisy-chained (concatenated) together using the D&I port, adding extra channels as required.
The Envoy supports up to 14 data channels without the need for concatenation.

There are two possible causes:

a) Incorrect Clock Master
The clocking may be set incorrectly. In any E1 system, one of the units must provide the master clock. Before the Echos were installed, it would have been one of the PABXs. It is CRUCIAL that the Echo which is connected directly to the MASTER CLOCK PABX be set to THROUGH clock. The other Echo should be set to LOOP clock.
When using an Elink 4 in Drop and Insert mode, both units must be set to Clock Source: Drop.

b) Incorrect SYNC mode (searching for CRC4 sync)
If the Echos are set to CRC4 synchronisation on the D&I ports, but the PABXs are not set for CRC4, the Echo’s will remain in CRC4 HUNT mode. This will pass calls OK for a while, but after a period of not finding full synchronisation, SYNC will be abandoned and re-started. Echo software version 1.05 and above will show a MAJOR ALARM by default if the units are in CRC4 HUNT mode.

You have probably not set the correct timeslot for drop and insert (D&I). Check the PABX documentation as to which timeslots it is programmed to use and then set the multiplexer accordingly.

PABXs use timeslot 16 exclusively for signalling information. This means you must set timeslot 16 for drop and insert D&I (even if you are using ADPCM). Once this is set all signalling information will go through and thus the corresponding phone will ring even if the correct voice channel has not been configured.

Normally the Echo uses the SA bits in timeslot 0 for communicating with the remote Echo so that you can configure both multiplexers from the same location. Some PABXs also use the SA bits for communication and can therefore become confused if Echos are introduced. Since Echo software version V1.05, you can make the SA bits transparent so that connected PABXs can use the SA bits exclusively for themselves without interruption. This feature can be turned on or off as required so that you can configure or monitor the remote Echo at any time if required.

The Elink 4 can be configured to use any timeslot (or none) for management though we recomend using Timeslot 0 if the SA bits are not otherwise being used.

The Echo does not affect the communication of PCM data between PABXs, therefore FAX and modem calls will pass through as before.

When using the ADPCM compressor, the speed of the FAX or modem may be reduced due to the ADPCM algorithm.

The Echo event log stores up to 960 events in a non-volatile 'ring buffer', i.e. when the event log is full, the oldest events get overwritten first. This information is stored even if power is interrupted. The event log records events such as synchronisation loss or power interruption together with a time stamp to aid fault finding. The event log can of course be reset when required.

The statistics display records the E1 link statistics history for the last 24 hours broken into 15 minute intervals. The statistics show any data errors which may have occurred on the line.