larry@uunet.uu.net (Larry Lippman) (10/08/89)
In article <telecom-v09i0418m05@vector.dallas.tx.us> portal!cup.portal.com! JDurand@apple.com writes: > I have been getting quite a few requests to add inbound pulse-dial (click) > detection to the voice mail boards I design. Since this is fairly easy to > do (we have two DSP's on the board, one dedicated to call progress), we will > be adding this to some future software release. The question is, we have not > been able to find any phone lines that allow the calling party to pulse dial > any number higher than 2 or 3 without dropping the line. Is this just local > to our area (GTE, Pac*Bell), or is this a widespread problem. I know there > is a company selling boards that just detect the inbound pulses, so there > must be some place it works. > Please note: I am not talking about loop current detect, just the sound of > the clicks transmitted through the network from the calling party. Most central office apparatus handling subscriber loop signaling requires a line open of at least 150 ms before disconnect. At a dialing rate of 10 pps with 60% break, the 60 ms line opens during dial pulsing are no where near long enough to cause a loop disconnect. The 150 ms timing is determined by one of the following, depending upon the type of CO apparatus: release time of slow-release "B"-relay in a trunk circuit; electronic timer equivalent of "B"-relay in a trunk circuit; or programmed loop supervision scan time in ESS apparatus. Therefore, theoretically, dialing into a completed connection with returned answer supervision should not result in a disconnect. However, from a practical standpoint, such a disconnect will happen, and ONE CANNOT ASSUME THAT PULSE DIALING INTO A COMPLETED CONNECTION IS A RELIABLE METHOD OF SIGNALING. The most common reason why disconnect will occur is maladjustment of DX signaling circuits and SF signaling circuits. Such maladjustment is generally undetected since it will not interfere with dialing PRIOR TO RETURN OF ANSWER SUPERVISION - which accounts for the ONLY type of dialing situation that a telephone company will ever consider. Pulsing tests and apparatus lineup on a DX or SF circuit are always conducted in the absence of answer supervision; after all, when you dial a normal telephone call, your dialing MUST be completed prior to answer on the far end! Properly balancing a DX circuit to pulse without distortion in the presence of answer supervision is much more exacting than balancing such a circuit to pulse without distortion in the absence of answer supervision. Improper SF level adjustments on an SF signaling circuit, such as an E-type or F-type unit, will also result in dial pulse distortion. Now, what happens is that the resultant dial pulse distortion causes an effective line open which is long enough to be interpreted as a valid CO apparatus disconnect signal. The above disconnect situation could not happen on a call where the interoffice trunk path was say, totally T-carrier, because signaling in the presence of returned answer supervision is not an adjustment problem on digital carrier apparatus. However, introduce a DX or SF trunk segment, and the problem is likely to occur. There is nothing that you, as a vendor of telephone apparatus seeking to interpret dial clicks, can do about this problem. It is beyond your control, and not an area which can be subject to any regulatory complaint. My personal opinion - which you can take with grain of salt - is to NOT offer this dial pulse detection option. The negative reaction of customers who become disconnected may well offset the positive value of this attempted feature. <> Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp. <> UUCP {allegra|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> TEL 716/688-1231 | 716/773-1700 {hplabs|utzoo|uunet}!/ \uniquex!larry <> FAX 716/741-9635 | 716/773-2488 "Have you hugged your cat today?"