The Block Signal No. 153 would change from GREEN to RED as a train approached. This was accomplished with the use of the No. 153C Contact that was placed beneath the track and changed the color of the signal indicator because of the weight of the train.

Carried over from pre-war production (1940-42), there are two major variations of this signal that occurred during the 14 years that this signal was being produced during the post war period.

Pre-war versions and early post war production had the numbers "153-3" (a casting number) and "NO. 153" inscribed on the base. With the introduction of the No. 151 Semaphore in 1947 that used the same base the "NO. 153" was eliminated and shortly thereafter so was the casting number.

The first major variation concerns the fact that early versions of this signal (1946-49) used 6 to 8 volt screw type lamps. To reduce the transformer track or accessory voltage (6-18 volts) to these lamps Lionel placed a resistor in the base of this signal.

The second major variation occurred in 1950. Lionel replaced the screw lamps with those that had bayonet base and used 12-14 volts so the resistor was no longer required.

An additional variation occurred in 1957 when Lionel switched from painted steel to aluminum for the signal posts. This version is lighter than those that were previously issued.

The block signal was always accompanied by a No. 153C Track Contact. The instruction sheet that was included with this contact was issued in envelope No. 153-61 for every year this signal was manufactured. First issued during the post war period under the No. 153-45 these instruction sheets are dated 10-45, 4-46 and 12-46. Lionel then changed the number of this sheet to 153C-18 for issues 3-46 and 11-46. This is highly unusual for Lionel to have two different instruction sheets that were available concurrently.

With the issue of 8-47 the number on the instruction sheet changed to No. 153C-22. See the No. 153C page for a detailed listing of these instruction sheets and a picture of the No. 153C-18 instruction sheet.

In April of 1953 Lionel issued a Correction Sheet No. 1312 amending these instructions. The wiring diagram that was on the orignal instructions is illustrated on the back page of Sheet No. 445-55 issued with the No. 445 Switch Tower.

There are three variations:

Variation A: Steel painted SILVER post, screw base lamps in signal head, resistor in base. Base has one, both, or no cast in numbers on the bottom. Nickel plated post finial that is sometimes found painted SILVER. 1945 to 1949 production.

Variation B: Painted steel post, bayonet base lamps in signal head, no resistor in base. No numbers are cast into the bottom of the base. Nickel plated post finial. 1950 to 1956, and 1958-59 production.

Variation C: Identical to Variation B except used an unpainted aluminum post. 1957 production.

Dimensions: 4" x 1-3/4" base. 8-3/4" high