atcomsystems.ca/forum Forums TDM Business Telephone Systems Mitel Telephones & Systems SX50 Trouble answering incomeing calls

Well this is another wierd one. SX50 system connected to a T1 via a channel bank.(an Adtran, I dont remember the model) 4 Ground start lines and has been working good for years. No problem calling out but we can only answer an incoming call if we hit the answer button while the trunk is ringing. If you hit answer between rings it just keeps ringing. I have tried it at the RJ21 with a butt set and have the same problem.If you stay offhook till the next ringing cycle it will answer as soon as the ring voltage hits. So far I cant convince the telco that they have a problem. When they come out and test at the RJ21 they clip there butt set tip to ring then apply a quick ground and go off hook at the same time to answer. It works every time that way. I have never applied a ground to answer a call on a ground start line but the telco says that is the way it should be done. They have changed the channel bank twice and I changed the trunk card in the system and even changed the entire system.
Three questions in this long post. Does the SX50 apply a ground to answer on ground start lines?
Next question, Have I been testing ground start lines the wrong way for over 30 years?? I am thinking something in the channel bank is not programmed like it should be. Anyone know what in the programming I should tell them to check.

Thanks

I've never had to apply ground to answer an incoming call. In fact, how many times have 'we' connected a 2500 set directly to a trunk, so customers can at least temporarily answer incoming calls while their PBX is down??

Check 5XX Register-4 Bit-C on all trunks. Make sure it's set for at least 6 seconds. This is assuming this is MS53/54/55.

Does this happen on all 4 trunks? It sounds exactly like a problem when polarity of the GS trunk is reversed. Can only be answered when ringing is present.

I will check 5xx-4 bit C. This is MS-55. It is on all 4 trunks. I have reversed polarity and then I could not dial out so I don't think it is a polarity problem. I have had the trunks changed to loop start for a tempoary fix. I did go to another location with ground start trunks and I could answer a call at the RJ21 at anytime in the ringing cycle by just going off hook.