M.C. Miller JR-2 Current Interrupter

Model JR-2 is a high power interrupter with 100 amperes DC interrupting capability.


M. C. Miller JR-2 Current Interrupter (Cat. # 12830)


  • 100 amp AC/DC interrupter
  • Crystal controlled timing
  • Rechargeable battery
  • Immediate or delayed interrupting operation
  • Low battery indicator
  • Capable of re-synchronization
  • On and off cycle times up to 999.9 seconds
  • Synchronization better than 1 second.

General Information

MCM’s Model JR-2 is a high power interrupter with 100 amperes DC interrupting capability. The JR-2 and JR-1 (35 ampere current interrupter) are of compatible “mix” when being used for multiple interrupter tests.



Custom LCD, wide operating temperature range, -20°C to +85°C (-4°F to +185°F) with enhanced response time at extremely low temperatures. Large(0.7″ high) digits plus equipment status annunciators.


CMOS Microprocessor, 8-bit; EPROM operating system. EEPROM, initializes prior setting on power up.


Sealed, Tactile feedback; 4×4 Matrix; “0-9”; “?”; “ENTER”; “CLOCK SET”; “START SET”; “ON CYCLE”; “OFF CYCLE” Keys.

Cycle Range:

Keyboard Programmable: 0.1 to 999.9 seconds in 0.1 second increments either “ON” or “OFF” cycle.

Auto Turn-on:

Preset interrupt start time eg. 0700

Night Latch:

The JR-2 supports 24-hour timing and a scheduled relay closure period. For example, a night latch time of 1700 could be entered from the keypad, and a start time of 0700. The unit will operate normally until 1700, at which time the relay will close and will stay latched until 0700 the next morning, then the normal interrupt cycle will begin again. This feature facilitates full CP polarization during hours when the survey crews are absent.


Timing: 0.5 second maximum variation in 24 hours. Synchronization to within 1 millisecond.

Relay Start Position:

Is in closed position.


Mercury Plunger Type

100 A @ 48 VDC 100 A @ 120 VAC
75 A @ 75 VDC 90 A @ 240 VAC
50 A @ 120 VDC 60 A @ 480 VAC
30 A @ 240 VDC 40 A @ 600 VAC

Sealed, rechargeable, 12 Volt, 6A/H Charging plug included.

Battery Life:

Depends on use.
Example: 1 second on – 4 seconds off yields battery life of approximately 50 hours.
Example: 4 seconds on – 1 second off yields battery life of approximately 15 hours.

Size and Weight:

10″ H x 10.75″ W x 5″ D
approx. 13lbs.


TCXO: Model JR-2Y: super accurate, temperature-compensated crystal/oscillator (1ppm). Timing remains constant through a temperature range of -40°F to 140°F. The crystal controlled clock operates at 1 MHz and is calibrated to have a maximum drift of only 1 part per million through-out the above temperature range. (Approximately 0.5 sec. in six days)

M. C. Miller JR-2 Current Interrupter