In 1869 Thomas Hall patented a two aspect electric railroad signal, it was a wood signal with a round cloth disc inside. Commonly known as the "Banjo" signal these signals quickly became the signal to use. With the invention of the track circuit in 1872 the use of the Hall Disc signals grew. The disc signals where nothing more than a wood case with a large round glass window in the front and back of the signal, A cloth disc would drop in front of the window to show caution for daytime indicaton, the disc would rise and the window would become clear to show the daytime indication of clear. A smaller round window was located above the larger and provided a night time indicaton with the same princials, a glass disc would block the window and a oil burning lantern would be attached to the back of the disc signal. At night the lamp would light the smaller disc for the indications. Since the disc signals were only able to convey two aspects, the railroads would add another signal below the top one to add another indication and another aspect. Disc signals were one of the most common signals upto the 1910's when semaphores became popular, later searchlights brought the best if the period and semaphores and disc signals were replaced. Disc signals where known to be around well into the 1950's. Some railroads retired the disc signals from block signals and turned them in to crossing signals.
Left and Right: Both Images from a 1901 Hall Signal Company Catalog.
The bridge behind the signal was Washington Street which at the time was wood. The bridge number was 58/39 which the bridge sign can been see to the right in this photo. The signals were removed in the 1940's and the bridge later replaced in 1964.
This rare color photo of the banjos was taken on May 18th 1947 near Reading, Pa. From the Jon R. Roma Collection.
The signal shown here was removed from service on November 20th 1942, the newly installed searchlight that replaced this signal can been seen down the tracks. This signal was located at Mile Post 54 near Neversink Road.
This signal replaced the old Hall Disc signal number 95 (pictured above) on November 20th 1942. In the background you can see 4 more Disc signals on a bridge, the new searchlight signals are already installed on the bridge to replace those disc signals.
Signal 102 as seen here has the new searchlights installed and is ready to replace the old Disc signals. You can see that they had to relocate the lower disc signal to make room for the searchlight. The disc signals were cutover November 20th 1942 and where located near Neversink Road.
Hall Disc Signals at Emaus Junction on 1949, note the mechanical semaphores.