Note
The HD-1515 is a fully solid-state device that utilizes an integrated active speech and transmission circuit. Direct connection to the phone line is made possible through a built-in active low voltage polarity-protection interface circuit. The HD-1515 derives its power directly from the phone line but may be battery operated with phone lines exhibiting low voltage conditions.
Special speech transmission circuits replace the conventional hybrid transformer and perform the 4-wire to 2-wire radio-to-phone line conversion. Front panel controls include power on/off, transmit gain, and receive gain. Connection to phone line is made via a standard RJ11 modular connector on the rear panel. The rear panel also provides access to line null controls.
Features include an 8-pole filter, PTT or VOX operation, and a built-in detector circuit for adjustment with a VTVM or VOM.
The HD-1515 is powered by the phone line or internal 9-volt battery. Caution: DO NOT install a battery unless it is needed. The HD-1515 works well enough but is a good example that more technology is not always better. Brown in color.
Telephone loop input impedance: about 600Ω, polarity protected
Receiver output (to phone line): not to exceed –9 db (278 mV)
Transmitter output (to radio equipment):25 mV into a 222kΩ load @ 1000 Hz
Receiver input impedance: 3 to 50 Ω
Transmitter (microphone) output impedance: about 22kΩ
Power requirements: telephone line powered, provision for battery if required
Photos, general information and specifications from "Heathkit: A Guide to the Amateur Radio Products," by Chuck Penson, WA7ZZE. Used with permission.
