Thread: Voltage fluctuations causing modem to reset EVEN with UPS

My modem & phone are connected to a UPS via a spike strip; whenever there is a voltage fluctuation or power outage for even a few seconds the modem reboots.

Is this normal ?

Happened to you is right.
Because, you failed to update the firmwire

Originally Posted by kattatu

Happened to you is right.
Because, you failed to update the firmwire

What rubbish? What has firmware to do with this?

@rsen, The modem is reseting because inspite of the UPS, there is a delay between UPS switching t battery power after mains failure. Check your UPS.

It is also possible that modem is old. Check the (external) DC power unit of the modem. Is it getting very hot? If required, change it.

@rsen

My modem & phone are connected to a UPS via a spike strip; whenever there is a voltage fluctuation or power outage for even a few seconds the modem reboots.
Is this normal ?

YES. Transient time 24 ms ( usual UPS)may affect modem.
Modem MT841
Power specs on the back of modem - 12 V AC 1.2 A
KTec AC adapter 12V 1200 mA
Please confirm modem you use is as given above..
IN which case 12 V D.C from UPS
battery can be directly connected to
the modem Power Input port.
Polarity of output plug cable should not matter.
Where the power adapter output is DC 12V= polarity in the plug will be marked say Inner positive.

( Built in AC to DC rectifier circuit in modem
will pass DC in Modem on H24 basis )

Suggestion:
Please Discuss before trying and wait for other member's comments..

thanks essbebe your help is always appreciated

modem - huawei MT81

other voltage/current values are the same as you specified.

im not sure about the ac/dc stuff - i have 1 phone and the modem connected to the UPS via a spike strip

@rsen
I have heard about this in other forums too, but don't recall where.

Noises can occur with both the electricity AC outlet as well as the phone line which also carries electricity but on very low voltage levels. This can occur especially under lightning and thunderstorms like Kolkata experienced yesterday.

(A few days ago while trying to cut the sheathing of the wires within the telephone Junction box with my teeth I accidentally shorted the two phases and believe me I did saw a white flash and remember the tingling in my tongue.)

Though the suggestions are costly, it will definitely guarantee you peace of mind

1. Either get yourself a Surge Protector from a reputed brand like APC or Belkin. Don't know about APC, but the Belkin gold series with 8o/p and dataline (i.e phone line protection) costs Rs1350/- at Ganesh Chandra Avenue (since you are from Kolkata).

Belkin : Gold Series 8-Socket Surge Protector

I haven't seen any APC surge suppressors in Chandni Area, but heard (read) they are superb too.

Read a good article about Surge suppressors here:

Anatomy of Surge Suppressors | Hardware Secrets

They also offer lightning protection upto 2444J I think which is excellent.

2.OR Get yourself an APC 650VA BE 650Y-IN UPS for aroun Rs3200/-. This too offers dataline or phone line protection and comes with AVR (Automatic Voltage Regulation). Beleive me it works even with modified (stepped) sine wave input when it runs on my el cheapo Numeric Inverter.

I got mine in exchange of my old APC BE500BY-IN for Rs3000/- from APC Service center near Triangular Park.
Lightning protection upto 180J I think (utterly insufficient).

see this diagram. From battery direct connect
T1 bypassed.

Originally Posted by babai

@rsen
I have heard about this in other forums too, but don't recall where.

Noises can occur with both the electricity AC outlet as well as the phone line which also carries electricity but on very low voltage levels. This can occur especially under lightning and thunderstorms like Kolkata experienced yesterday.

(A few days ago while trying to cut the sheathing of the wires within the telephone Junction box with my teeth I accidentally shorted the two phases and believe me I did saw a white flash and remember the tingling in my tongue.)

Though the suggestions are costly, it will definitely guarantee you peace of mind

1. Either get yourself a Surge Protector from a reputed brand like APC or Belkin. Don't know about APC, but the Belkin gold series with 8o/p and dataline (i.e phone line protection) costs Rs1350/- at Ganesh Chandra Avenue (since you are from Kolkata).

Belkin : Gold Series 8-Socket Surge Protector

I haven't seen any APC surge suppressors in Chandni Area, but heard (read) they are superb too.

Read a good article about Surge suppressors here:

Anatomy of Surge Suppressors | Hardware Secrets

They also offer lightning protection upto 2444J I think which is excellent.

2.OR Get yourself an APC 650VA BE 650Y-IN UPS for aroun Rs3200/-. This too offers dataline or phone line protection and comes with AVR (Automatic Voltage Regulation). Beleive me it works even with modified (stepped) sine wave input when it runs on my el cheapo Numeric Inverter.

I got mine in exchange of my old APC BE500BY-IN for Rs3000/- from APC Service center near Triangular Park.
Lightning protection upto 180J I think (utterly insufficient).

I already have an APC backup AVR UPS. My phone and modem are connected to it via a spike strip.