In a message dated 96-06-01, 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. > > Duane:
David Drori has already made an excellent response, so I will only add a few remarks: 1) The Meder rep in the USA is Gary Miller at GEM Electronics, 401-885-8454. 2) Both reed relays and the Toyocom hybrid introduce some series inductance. This can sometimes influence insertion loss, especially at billing tone frequencies. Test this parameter carefully for your target countries. 3) You can use an opto circuit for loop current detection in France, but watch out for the French "insertion loss" requirement on ringing voltages (2 volts max). 4) I wrote an article on the new B1123A spec in France in the January/February issue of Compliance Engineering. In that article, I discussed the problems with loop current sensing in a section called "Series Connections". There are several parameters that are affected by the loop current detector, and meeting all of them simultaneously for France was difficult in the past. In B1123A, however, the requirement for detecting loop current has been eliminated. This gives you much more flexibility than in the past. I hope this helps you get pointed in the right direction. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc.
