The Modular Half Line Terminator terminates a telephone line or analog station port at voice frequencies, changing the impedance of the line.
Some equipment only works if there's a load on the line and adding one of these can be easier and less expensive than adding a phone or other device.
The Modular Half REN Line Terminator has proven to be very valuable for fixing voice mail and faxback DTMF and CNG tone recognition problems!
Connects in-series with a modular jack and plug (RJ-11), between the telephone line or analog station port, and the telephone equipment.