Zaptel advanced configuration

I’ve got gsm <-> pstn gateaway and would like to connect it to my * box. When connect it to analog pbx it works ok. (I dial the number of gw from phone, gateaway answers and I get the dialtone to dial the number). The problem is when I connect it to the FXS (tdm400p) of my * the gateaway answers immediately.

Consequently, when I try use the gateaway ZAP/4 is always busy. Using ztmonitor I see that * just after the connection to gw sends and gets tone and after 20-30 secs begins to send busy signal.

So why does * begin to use the channel. Can I hangup it manually? Maybe I can somehow to connect to it (smth like making a conference). What’s the difference between FXS of analog PBX and FXS of tdm400p?
I have no idea what to do. Please, help.

there shouldn’t be ringing on the FXS port if you’ve only connected it !! does the GSM gateway have 2 ports, 1 for trunk-side, 1 for extension-side ? if so, is it connected correctly ? what gateway is it ?

It has only one port and it should be connected to the line. So it’s like analog phone.
The gateway is noname but as I’ve written it works ok with the analog pbx. After 5 secs it answers and you can dial any phone number using GSM network.
I’ve connected it to ZAP/4 of my tdm400p. (It’s configured correctly because I tested with analog phone and it worked fine). Then I added to extensions.conf:
exten => 280,1,Noop(Dialing ${EXTEN})
exten => 280,n,Dial(ZAP/4, 20, tT)
exten => 280,n,HangUp()

I expected that after I dialed 280 the gateway answered and I could use gsm network.
I can’t, because it’s always busy :frowning:. It’s always offhook.

Sorry for my English.