Technical Manual

Technical Manual AM Systems
AM operating principle v4.4 Page 13 of 72
5.1 Synchronization principle
When multiple AM systems are installed in each other’s vicinity, it’s very important to
properly synchronize the transmission burst and receiver windows for all systems
involved. If systems are not properly synchronized they will create false alarms and poor
detection! Keep in mind that AM signals, when compared to other EAS technologies, can
“travel” quite far (up to 100m or more) because of their longer wavelength.
Figure 2 shows two AM systems that are not properly synchronized.
Figure 2: Two AM systems NOT synchronized
The transmission burst of system B starts later than the burst of system A, resulting in the
fact that system A is receiving the transmission burst of system B in its receiver window.
This might create false alarms and poor detection on system A, where system B will
function properly as the transmission burst of system A is not affecting the receiver
window of system B.
This problem can be solved by making sure that both systems transmit and receive at the
same moment, which can be realized by changing the delay time for one of the two
systems.
Example:
System A has currently a delay time of 0.2ms and system B a delay time of 1.4ms. The
delay time of system B needs to be corrected to the delay time of system A (or vice
versa), so their mutual transmission burst and detection windows will overlap each other
(see Figure 3). This will result in both systems working properly without interference (see
Figure 4).
Transmission burst
Receiver window
Reference window
20ms
0ms
Transmission burst
Receiver window
Reference window
System A
System B
50Hz mode