The digital selective calling systems ZVEI and VDEW were defined for selective call and data transmission in the non-public mobile land radio service. The ZVEI system adheres to the recommendation AK SRDS 87-3D, while the VDEW system was known as DIN45013 until 1992. The systems are identical on the physical layer. Due to the special requirements of the VDEW some additional features where added to the ZVEI system.
|
Parameter |
Value |
|
Frequency range |
VHF/UHF |
|
Operation modes |
Digital Selcal |
|
Modulation |
FFSK |
|
Symbol rate |
1200 Bd |
|
Center frequency |
1500 Hz |
|
Shift/Bandwidth |
600 Hz |
|
Receiver settings |
FM, BW = 12 kHz |
|
Input format(s) |
AF, IF |
|
Additional Info |
BCD-Code, ZVEI and VDEW digital selective calls differ in codeword interpretation and BAK |
In the VDEW system it is possible to concatenate up to four telegrams. The basic telegram (Grundtelegramm) is followed by one or more follow-up telegrams (Folgetelegramme).
The difference between both systems is the BAK (Betriebsartenkennung). VDEW uses the BAK to indicate follow-up telegrams, ZVEI does not. The BAK for the whole message is transferred in the last follow-up telegram. By means of the BAK the decoder detects if it is a VDEW message with follow-up telegrams.
The transmission speed is 1200 bps and the FFSK nominal frequencies are 1200 Hz for logical '1' and 1800 Hz for logical '0'. Indirect modulation (sub carrier) is used. A data packet consists of 64 bits. After a carrier pre-keying, an 8 bit telegram preamble and a 15 bit Barker sequence follow. Data is protected by using 8 bit redundancy.
Mode labeling for ZVEI and VDEW (BAK:)
There are 16 different values for the various call types:
|
Parameter hex |
Value ZVEI (first data word) |
Value VDEW (following data words) |
|
0 |
User defined |
Not used |
|
1 |
Call to mobile |
Call to mobile |
|
2 |
Call to base station |
Direct Access |
|
3 |
Identification |
Identification |
|
4 |
Acknowledgement |
Acknowledgement |
|
5 |
Spare (indicate VDEW) |
Sequence telegram |
|
6 |
Separation call |
Separation call |
|
7 |
Spare |
Recall |
|
8 |
Priority call |
Emergency call |
|
9 |
Status request |
Status request/response |
|
A |
Spare |
Position request |
|
B |
Acknowledgement |
Acknowledgement |
|
C |
Spare |
Quick dialing |
|
D |
User defined |
Data |
|
E |
User defined |
Spare |
|
F |
Emergency call |
Not used |
Status for ZVEI and VDEW (STAT:)
Four bits are available. In the VDEW system these four bits indicate the number of follow-up telegrams. The last follow-up telegram and a basic telegram without follow-up telegrams are indicated by 0xA. In ZVEI the status bits can be used by the carrier.
Rhombic labeling (RAUTE:)
Four bits are used as additional distinction for a producer designation. The use is not determined.
Manufacturer identification (Herst:)
Two digits are used. The classification is determined by ZVEI.
In the newer VDEW system the rhombic labeling and the manufacturer identification are combined into one field of three digits, called EVU number (EVU#:).
Call number ZVEI and VDEW (Ruf#:)
Three digits are used. The hundred-position digit is transmitted first, the one-position digit last. Group calls are transmitted as pseudo-tetrads of '1111' (16). For a group call in the 10s range the digit representing 1s is filled with logical ‘1’. For a group call in the 100s range, the 1s and 10s digit are filled with logical ‘1’, and for a 1000s range call all 12 bits are filled with logical ‘1’.
EVU and call number are transferred in a block of six digits. The partitioning is either 3 digits for either items or 2 EVU digits plus 4 call number digits. The chosen variant cannot be derived from the data, so both versions are displayed.
The following picture shows a trace of a VDEW transmission with basic telegram and a single follow-up telegram, displaying both versions of partitioning, i.e., 3 + 3 as well as 2 + 4.
The next picture shows a transmission which can be either a ZVEI message or a VDEW message without follow-up telegram.
The user has to decide from the context which transmission standard was used. In case of a VDEW transmission without follow-up telegram, the rhombic labeling and the manufacturer identification have to be interpreted as EVU#.