Dear TREGers, Duane Marcroft writes:
" I need help! Has anyone used a current relay to sense loop current in a French DAA? I need the name of a vendor with a reed relay that can be used to sense loop current when the handset connected to the modem is off-hook. B11-23A allows too little voltage drop to use an opto. To insure the detection of line current and and not add too much insertion loss between TIP and RING of telco RJ-11 and handset RJ-11 I need to use a reed relay. Some people refer to this as series insertion loss of the TE." I understand that the original French requirement for 5 mA series detection sensitivity, specified in NET 4, has been relaxed in B11-23A. This makes it easier to design the series current detector, since reed relay detectors are not sensitive enough for 5 mA applications. I do not know what the exact figure is for B11-23A. However, assuming that a 15 mA must-operate current is acceptable, then you could use the DIL-CL-1A81-9-13M from: Meder Electronic GmbH, Robert-Bosch Strasse 4, D-7700 Singen/Hohentwiel, Germany. Tel: +49 7731 62002 (or +49 7731 83990) Fax: +49 7731 66524 (or +49 7731 839930). The DIL-CL-1A81-9-13M relay has the following relevant characteristics: Coil resistance: 9 ohms Must operate current: 15 mA Must release current: 5 mA Isolation: 3 kV AC, 4.25 kV DC Coil inductance: 3.2 mH. I'm afraid I don't have details of Meder's representative in the USA. However, in the UK, you may call: Willow Technologies Ltd., Shawlands Court, Newchapel Road, Lingfield, Surrey. Tel: +44 1342 835334 Fax: +44 1342 834306. Another possible solution is based on a Hall effect device called a "Current Sensor", from Toyocom, designed specifically for the kind of application you mention. Two of these devices were recommended for the older, more stringent, French requirements; namely, the THS-68 and THS-62, at 437 Yen in 10K quantities (CIF). The advantage of the Toyocom devices is that they are more sensitive than reed relays, and the above-mentioned types will respond to 5 mA. The contact at Toyocom is a Mr. Takagi: Toyocom, Toyo Communication Equipment Co. Ltd., 12-32 Konan 2-chome, Minato-ku, Tokyo, 108 Japan. Tel: +81 3 5462 9600 Fax: +81 3 5462 9625. Since there was no agent in our country, we had to deal directly with Toyocom and found them very pleasant but difficult to deal with. It took several months and much correspondence about our company, plus a D&B investigation, just to obtain a few samples! We originally contacted Toyocom USA Inc., at fax number (708) 593-5678, and our request was passed on to the above-mentioned office in Tokyo. If the 5 mA requirement has really been dropped, and the Meder relay is sufficiently sensitive, then this is probably your best bet. Reed relays are also available form CP Clare. The type you need is known as "Line Loop Relay - Current Sensitive Version" and is produced in a number of models, for 8 mA or 15 mA must-operate currents, and with coil resistances ranging form 10 to 46 ohms. The 8 mA variety has a resistance of 46 ohms. Yet another source is Aleph who make "PCS series current sensing relays", with a must operate current of 13.5 mA and a coil resistance of 6, 8 or 10 ohms. Contact details are as follows: USA: Aleph International Corporation, 1026 Griswold Avenue, San Fernando, CA91340, USA. Tel: (818) 365-9856 Fax: (818) 365-7274 Europe: Aleph Europe Ltd., 1 Newton Close, Park Farm Industrial Estate, Wellingborough, Northamptonshire NN8 6UW, England. Tel: +44 1933 679600 Fax: +44 1933 401165 I hope this information is useful to you. I am always on the look-out for devices that will help meet the special requirements for analog telephone interfaces throughout the world. Therefore, if you discover anything new on this subject please don't forget to update me. At any rate, I'd be interested to know what you eventually choose and the cost. Also, if anyone else on TREG has additional information, we would also be glad to hear it. Best regards, David Drori ----------------------------------------------------------- Novarex Enterprises Ltd., POB 2833, 306-6, Mevo Hapartisanim Street, Jerusalem 91028, Israel. Tel: +972 2 810995 Fax: +972 2 813750 -----------------------------------------------------------
