There's an HP 5061-1136 Return Loss Bridge 124? 10KHz-10MHz on ebay at :
-- 73 Hank WD5JFR
The dual plug on the side and the empedance looks like typical telco equipment
Bill K7NOM
As Bill noted, it's telco. Looks like something we used to make, or at least supported at the end of its life. I suppose a 3-decade frequency range isn't extreme, but I'll bet it's more (for the achieved performance level) than most hams get in homebrew directional couplers. ;-) It's possible I could find more info on it if you're seriously interested.
Cheers, Tom
The frequency range, the empedance and the plug, all point to use with "L" carrier analog multiplex. The 124 Ohm would be a balanced line and consist of a shielded pair. I don't know if 124 Ohm single conductor shielded cable was used
Bill K7NOM
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