Motorola MTP3550 TETRA Portable Radio – Experience #9: All Call/Open Group (全呼) скачать в хорошем качестве

Motorola MTP3550 TETRA Portable Radio – Experience #9: All Call/Open Group (全呼)

Here I am transmitting an All Call (TETRA calls it "Open Group") with each of the radios. This function is extremely useful. For example, if you see the orange LED on your radio lights up, it means someone is using the same DMO frequency in your vicinity. However, you may not know who/where he is, and what the parameters of his DMO channel are. In order to approach him (just to say hi or further exchange communication methods), you can use this "All Call/Open Group". - Similar to DMR, TETRA also adopts the magic number of "16777215" as the GSSI for All Call/Open Group. In order to transmit an All Call, configure a DMO channel with GSSI of 16777215. As such, another radio at a different talkgroup will receive the transmission from GSSI 16777215, provided that both radios are on the same frequency and MNI. This is what makes it "All Call". - This video first shows the behaviour of radio when it encounters a transmission from a mismatched GSSI. During a transmission in DMO, it occupies the frequency. Other channels (even with other GSSI/MNI) will not be able to transmit until that occupied frequency is released. This is indicated by the orange LED on the radio, meaning that the frequency is occupied. If the radio keys up, it establishes no transmission and its display will show "Channel Busy". - Unlike DMR, All Call in TETRA allows response to the call itself. That is, an All Call does not end upon the release of PTT. It actually ends after the "DMO reservation time" has expired. - With that being said, if Radio A (GSSI 1234 for example) tries to response to the All Call given by Radio B, and Radio A keys up within the DMO reservation time of that All Call, then Radio A will be able to "pick up" that All Call and continue transmitting on it. However, if Radio A keys up after the DMO reservation time of that All Call has passed, then Radio A will be transmitting on its original GSSI (1234 in this example) when it presses its PTT. It is because the previous All Call ends when the DMO reservation time has expired.