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VG224 - MAXIMUM DISTANCE

alicia.vega
Level 1
Level 1

Is it any problem in connecting an analog phone to a VG224 with a 2,5 kilometres cable?

Thank you very much!

3 Replies 3

Imran Khan R
Cisco Employee
Cisco Employee

FXS Analog Voice Port Maximum Distance:-

=================================

The maximum distance is established by a total allowable loop resistance, including the phone or terminal equipment, of 600 ohms.  Our FXS interface meets OPS Class B specs. Specifically, we can source greater than 20ma to a resistive distance of up to 1100 ohms. The homework question is translating impedance to actual distance in meters in your customer's environment; which will depend on the gauge of the wire as well as how the wire is routed and punched-down. It will depend on the type of phone/equipment you are hooking on the line as well as to how well it will work.

Also found how to calculate the dc loop resistance:-

======================================

Calculating dc loop resistance

LRi = CRi * SLi

where LRi= DC loop resistance for cable section

CRi= Conductor Resistance per unit length for the cable section ( used gauge 24 rj11 cable)

Sli= length of cable section

Lri =600ohms

CRi = 173 ohm/loopkm

SLi = ?

= 600 ohm/ 173 ohm/loopkm

= (600 / 173 ) loop KM

= 3.47KM

= 3470 * 3

= 11384 feet.

So the FXS on the VG 224 using a gauge 24 cable (RJ-11) would allow for a max loop distance of 10410 feet .

rshaltie
Cisco Employee
Cisco Employee

Hi,

In your calculation, the maximum distance is established by a total allowable loop resistance should be NOT including the phone or terminal equipment.

so the 600 ohms in total - 430 ohms of the phone = 170 ohm for line resistance

CRi = 173 ohm/loopkm

= (170 / 173 ) loop KM

=0.98 Km

Alicia,

Looking at the VG224 datasheet

http://www.cisco.com/en/US/prod/collateral/voicesw/ps6790/gatecont/ps2250/ps5516/product_data_sheet09186a00801d87f6.html

Category

112-FXS Bundle

VG 224

VG 204/VG 202

FXS Loop Length

3000 ft, 26 AWG

3000 ft, 26 AWG

3000 ft, 26 AWG

You should will be out of reach at 2.5 KM

3000 feet is approx 1KM

Regards,
Alex.
Please rate useful posts.

Regards, Alex. Please rate useful posts.
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