Hi. Thanks for the reply!!
Let me explain properly what I meant about half duplex comms. At present we have 6 digital radios(frequencies) at our remote site which is connected to our main site through IP Link (IP VPN MPLS). These remote radios need to be communicated with our voice switch at main site. The communication interface for both radios and voice switch is E1 ie we want to have communication between voice switch and remote radios through routers having E1 cards. All radios are connected to a E1 card on our Vanguard router and routed through MPLS cloud to our main office where we take it from an E1 card to our voice switch. Each of the 6 frequencies is assigned a timeslot on the E1 and the idle state is set to 0101. When one of the air traffic controllers keys the remote radio(PTT) the TX code 1010 is sent to the remote side and the radio gives the squelch code of 0011 back which means the radio has opened the path for transmission from voice switch to antenna and the controller can speak to the pilot. At this time, ideally the receive path from pilot should be closed ,ie. half duplex, but the E1 card was , by default, set to full duplex and this caused feedback as the rx path was still open when the controller was sending a transmission. Vanguard then changed their software to half duplex so that when a controller PTT's the remote radio only the transmit path is open and on the other side, when pilot keys the mike, only rx path become open and not tx path. This cleared the feedback problem we had.
For reasons I don't want to get in to I'd rather use Cisco but I would like to know if the above mentioned is possible before purchasing E1 cards only to find out we're stuck with the feedback problem.
Cheers!!
