Generators and Accessories
The 181 is the “little” brother of the Type 180A Time-Mark Generator. This one I have is not a cabinet model but a rack-mount type (so RM181..). It is equipped with an temperature-stabilized crystal “crystal oven” and therefore the RM181-MOD 110 provides a marker stability of 3 parts per million (ppm) over 24 hours. I took the specs out of the catalog 24 (1965/66). The RM 181 cost about $290 that time the RM181-MOD 110 was rated at $310. You could buy the oven as an accessory for about $27.
The repair hints about the RM181 will follow soon...enjoy! Please look in the Tube Testing & Repair Hints section...