Full-duplex?

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Tophtoh

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The CIS system is a full-duplex radio system. what does this mean? i see there is only an output frequency listed. does this have something to do with it? thanks!
 

SkipSanders

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'Full Duplex' means that each direction of communication can happen at the same time.

Normally, that means at least two frequencies (or channels, of something tricky in TDM is up so there's more channels than frequencies).

Full Duplex means Mobile can be talking to the Base, and the Base hearing them, at the SAME TIME the base is talking to the Mobile, and the mobile is hearing the base. Like a normal telephone.

Half-Duplex means only one way at a time. There may be two frequencies, but when one end is talking, they can't hear the other end if it also transmits at the same time. Actually, it's usually the Base than has priority in this. If the base is talking, all mobiles can hear them... unless they're trying to talk at the same time, in which case they can't hear the base. Sometimes, it's more complex, and if a mobile transmits while the base is talking, other mobiles can't hear, but the base may be able to tell there's an attempt to break in, by hearing it on remote receivers, etc.

Simplex, one channel. Again, one way at a time, but if both try to talk at once, NEITHER hears the other.
 

Tophtoh

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its in the toronto page. the for toronto city buses. thanks for your reply this help. may i ask do you know how trunking systems work? are they full, half or simplex?
 

fineshot1

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Tophtoh said:
its in the toronto page. the for toronto city buses. thanks for your reply this help. may i ask do you know how trunking systems work? are they full, half or simplex?
Trunking systems are multi-channel computor controlled full duplex repeater systems. The only simplex repeaters are the "voice store & forward" types but I don't think there are too many out there these days(watch a bunch of RR users jump on me for saying that).
 

n2mdk

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fineshot1 said:
Trunking systems are multi-channel computor controlled full duplex repeater systems. The only simplex repeaters are the "voice store & forward" types but I don't think there are too many out there these days(watch a bunch of RR users jump on me for saying that).
Trunking system like all repeater based systems are half duplex, full duplex systems are like telephones they receive and transmit at the same time. If it uses a PTT it can only be half duplex at most.
 

fineshot1

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n2mdk said:
Trunking system like all repeater based systems are half duplex, full duplex systems are like telephones they receive and transmit at the same time. If it uses a PTT it can only be half duplex at most.
Huh??? Check again. Repeaters are full duplex. That is - they transmit and receive at the same time. They receive on the input frequency at the same time the transmit the received audio on the repeater output frequency. A trunking system consists on multiple repeaters that are controlled by a computor or actually its just called a controller.
 
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DaveNF2G

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"Half" or "full" duplex are defined according to what the user can do.
 

kb2vxa

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Fine, you're missing the point. Telephones for example (hard wired, portable and cell) are full duplex, you can still hear the other party while you're talking and there is no push to talk, no need for it. Nextel may be an exception, I'm not familiar with it.

For what it's worth the only full duplex repeaters I have heard (there may be others) were VHF ship to shore marine and the old Bell Mobile radiotelephones before cellular service was invented. BTW, only the very expensive marine radiotelephones could use the repeaters in full duplex mode, most boaters used standard marine radios and the repeaters in half duplex.

Like the man said, anything with push to talk can be only simplex or half duplex, only one unit can transmit at a time. Sometimes they forget and talk over the dispatcher or each other and nobody gets through but that's life without proper training. That's why I get a laugh at a dispatcher calling out "somebody has an open mic" when the one with the button down can't hear a thing.

No Dave, it's defined according to what the repeater is capable of as I have just explained. You just didn't see it as we were typing at the same time and beat me to the post. (;->)
 
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loumaag

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Okay, enough of the "see above".

Actually although the repeater (either conventional or trunked) simultaneous repeats the input signal, the terms "full-duplex" and "half-duplex" deal with how communication happens, not what a repeater does. Hence, trunked systems are half-duplex as are almost all standard repeaters. Telephone's (all kinds) are full-duplex (effectively). Most radio systems are half-duplex. Simplex really doesn't exist except as term invented to note there is no repeater used.
 

fineshot1

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OK - Let me re-state my position and this time I'll dot my I's and cross my T's.

The OP reffered to the "Toronto CIS System", which when I see the word "system"
I usually think of the network infrastructure and in this case that basicly means
the repeaters and there support equipment which is "full duplex" despite that fact
that a repeater(conventional or trunking) uses PTT in order to transmit.

Yes - the mobiles, portables, control stations, whatever, are "half duplex" but I was
not even considering them since I thought we were discussing the "system" and
not the end user equipment.

I hope that clears up my posts in this thread. :)
 
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