Analog/digital gateways ?

[lavanya_cisco]

Hello all,

I'm really new to IP telephony infrastructure. Sorry for bugging you all with some silly questions..

Anyway, I was reading about call manager integration with Voice gateways, and as I know there are analog (PSTN) and digital gateways (ISDN). what are the practical scenarios to select an analog or digital gateway ? How do we select the gateway model in accordance with the signalling method ?? Can anyone give me some practical examples on the gateway/signalling selection ?? When do we give customers analog and when digital solutions ?

thanks

[teodorgeorgiev]

Most often, you can't decide. It is the Telco or or the PBX which "decides". You just choose a gateway that can match their protocol / port type.

If the local Telco offers only analog ports, you buy an analog gateway. If they offer an E1 with R2, you buy a sigital gateway that supports R2.

[Chris Deren]

Well it all depends on the call capacity you require. If you need large number of calls then you'd look into CCS (common channel signaling) such as PRI, QSIG which provides 23 barrier chanels and delta channel for signaling on T1 and 30/2 in E1. Older digital technology is CAS (channel associated siganling) which provides inband signaling and gives you 24 timeslots on T1.

Analog signaling such as FXO, FXS, E&M, DID provides single port per cable,for example your home phone line.

If you have a small office for example and require only 4 phone lines, you would get 4 POTS lines which are analog.

Hope this helps.

Chris

[lavanya_cisco]

Thanks chris.. really a useful info.. thanks again..

[teodorgeorgiev]

As I see you are in India, so you should pay more attention to the R2 signalling protocol. It runs over E1 link (30 ports). Your Telco provides analog phone lines and R2 digital lines.