Chapter 6 Using the Station Channel

Click Topic for Quick Find:
1. What is the maximum length of a station phone line from the station module on an analog board?
2. Why does the station channel constantly appear to be in “off-hook” or “idle” state?
3. Why does the station phone connected to the station module sometimes ring for no reason?
4. Why does the station channel detect an “off-hook” signal while the station module causes the station phone to ring?
5. Can the external power supply for B-type boards be used for C-type boards, and vice versa?
6. When a station phone makes a call from a station module via an analog trunk channel, the volume heard at the remote phone sounds rather low. Why?
7. How to transfer an incoming call to an analog trunk channel to a call-agent?
8. How to send CallerID via a station channel to a phone that can receive CallerID?
9. Two station channels and a trunk channel join the same conference. When one of the station channels plays sound with a station phone on-hook, other channels can still hear the sound played. Why?
10. Why does a station phone hear howling when it makes a call from a station module connected through a trunk module?
11. Why is there much noise when the station phone connected to an on-board station module is off-hook?


1. What is the maximum length of a station phone line from the station module on an analog board?
It should not exceed 4.8km.

2. Why does the station channel constantly appear to be in “off-hook” or “idle” state?
If the station channel is constantly showing “off-hook” when the station module is not connected to a phone, or showing “idle” when the connected phone is off-hook and the power indicator is on, it could be that the connection between the module and the board is loose or the station module has been damaged in transport.

3. Why does the station phone connected to the station module sometimes ring for no reason?
This could be due to poor line quality or improper board grounding.

4. Why does the station channel detect an “off-hook” signal while the station module causes the station phone to ring?
This is mostly due to the security lock function which is available on certain station phone, and can be resolved by unlocking the security system.

5. Can the external power supply for B-type boards be used for C-type boards, and vice versa?
Yes, because B-type and C-type station boards have the same external power interface and interface parameters. This power supply is called Ringing Current & Battery Feed Power Supply.

6. When a station phone makes a call from a station module via an analog trunk channel, the volume heard at the remote phone sounds rather low. Why?
This can happen in communication between a station phone and a toll phone and can be resolved by adjusting the volume on the bus which connects the station module and the trunk module.

7. How to transfer an incoming call to an analog trunk channel to a call-agent?
1) When the trunk channel detects ringing, the station channel invokes the function SsmStartRing() which causes the station phone to ring.
2) When the station channel senses that the station phone is off-hook, the corresponding trunk channel invokes the function SsmPickup() to pick up the call.
3) Invokes SsmTalkWith() and connects the off-hook trunk channel with the station channel through the bus. The trunk now talks with the station.

8. How to send CallerID via a station channel to a phone that can receive CallerID?
1) For DTMF: The station channel can invoke the function SsmTxDTMF to send CallerID before the first ring.
2) For FSK: The station channel can invoke the function SsmStartRingWithCIDStr to send CallerID.

9. Two station channels and a trunk channel join the same conference. When one of the station channels plays sound with a station phone on-hook, other channels can still hear the sound played. Why?
With the station phone being hung up, sound played by the station channel reaches other channels as echo from the phone, which is why other conference channels can hear the played sound.

10. Why does a station phone hear howling when it makes a call from a station module connected through a trunk module?
When a station module is directly bussed with a trunk module, and the station phone is off-hook while the trunk module remains on-hook, dissimilarity of impedance levels will cause howling to happen in a call. This can be resolved by invoking a function to link the station channel with the trunk channel over bus, while both are off-hook.

11. Why is there much noise when the station phone connected to an on-board station module is off-hook?
This usually occurs with poor contact, bad lines, improper grounding or even interference from the power supply.