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New Member

E1 voice card


Could you kindly assist with the following?
Do the Cisco VWIC-1MFT-E1, VWIC-2MFT-E1 cards support half duplex communications? We have VHF radios at our remote sites which our guys can access through a Vanguard router. Each timeslot carries a specific frequency(radio) and the E1 card is configured as half duplex to eliminate any feedback. 

  • Unified Communications Applications
Hall of Fame Super Gold

Re: E1 voice card

There is no concept of half duplex in digital telephony.

Router will act as if connected to any other system.

If you want to learn about the opetions you have to connect VHF systems, read "land radio white paper", found via CCO search box.

New Member

Re: E1 voice card

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.


Hall of Fame Super Gold

Re: E1 voice card

Again, E1 with Cisco doesn't have that choice.

And the matter of E1 CAS also should be tested as an issue in itself.