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Community Member

Siemens PBX(E&M) with Router 1750

Hi all,

I had a problem with my cisco 1750 router connecting to a Siemens PBX(E&M i/f). The problems are:

1) Calls from outside can reach the router and be routed to individual phones via the PBX(E&M), except that the connection time only lasts for a few minutes(1 ~ 5, quite random)

2) Cannot make outgoing calls.

Seems strange on why incoming calls are OK but cannot make outgoing calls at all, and the connection time only last for a while.. Does it matter with the router IOS version(I'm using c1700-sv3y-mz.121-3.T)? Also I wonder if I must ground the grounding screw(beside the AUX port on the back side) to the PBX's ground? Or can I do something to verify the router..?

Apprecaite your experiences in advance!!


Community Member

Re: Siemens PBX(E&M) with Router 1750


Could you send me details of your router config?



Cisco Employee

Re: Siemens PBX(E&M) with Router 1750

If your calls are disconnecting after 3 min, you are not getting answer supervision. The signal ground for analog e&m ports is on pin 8 of the RJ-45 is best practice to make sure you have a common ground with the PBX for analog e&m applications. Here are some links that may help:

Hope this helps,


Community Member

Re: Siemens PBX(E&M) with Router 1750

Thanks Colin and Chester,

The problem was finally solved by "shorting" the router ground with the SG of individual voice ports on the E&M module. Really strange as router can only detect both on/off hook and send/receive digits after the hard-wiring.... But still need to check if this may have side-effects such as burning the line cards....



P.S. Below is a partial router config:


voice-port 1/0

echo-cancel coverage 32

cptone CN

timeouts interdigit 4

timing percentbreak 60

operation 4-wire

type 5

signal immediate


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