SCR-536 Walkie Talkie
The Motorola SCR-536 was the original walkie talkie (called handy-talkie at first, see Note below). It was the smallest of Signal Corps radio transmitter and receiver sets in World War II. The same equipment is often called BC-611 for its main radio unit.
Radio Set SCR-536, the smallest Signal Corps transmitter/receiver of World War II.
The Olive-Drab.com Historical Military Photo and Poster Gallery includes a photo of an Airborne Infantry Officer with an SCR-536 Radio Set.
Radio Set SCR-536 (and the -A to -F modifications) consists of a five tube, low power (for its time), dry battery operated radio receiver and transmitter, plus certain accessories. It is designed for amplitude-modulated (AM) two-way communication over short distances. The outstanding feature of its design and constructions is its extreme portability (again, for its time -- very bulky by today's standards.) It is intended primarily for foot combat soldiers to communicate with their commander or with supporting units. In the photo to the left, PFC Harold C. Schreckengest, CO's runner, is using an SCR-536 to direct movements of Company E, 2d Battalion, 2nd Infantry Division, U.S. First Army in Koenigsfeld, Germany, 9 March 1945.
The core component is the BC-611 Radio Receiver and Transmitter, sometimes confused with the entire SCR-536 system. The SCR-536 operated over the 3.5 mc to 6.0 mc frequency range on any one of 50 channels. Plug in crystals and coils were used to control the frequency of the receiver and transmitter. The range of the unit was about one mile over land and perhaps 3 miles over ocean. The antenna was a 40 inch telescoping rod that slid into the case. The unit weighed 3.85 pounds without batteries.
There was no power switch on the SCR-536. The operator pulls out or pushes in the antenna on the top to turn the radio on or off. The power was supplied by a BA-37 1.5 volt dry battery for the filament supply and a 103.5v BA-38 battery for plate supply. Battery life was about one day of normal use. The two batteries weighed about 1.6 pounds.
The technical manual was TM 11-235.
A special version of the SCR-536 was produced for use in glider aircraft. Radio Set SCR-585 (with BC-721 Transceiver, in A and B variants) was dual use. It could be carried as a hand-held radio, exactly like the SCR-536, but it also came with a mounting system, remote pull-to-talk control, and other modifications for fixed installation to serve a glider pilot and co-pilot. Connections are provided for two headphones and one throat microphone. A sliding door on the case, above the PTT switch, opens to connect the glider antenna to the SCR-536.
The very popular SCR-536 AM set was followed by tropicalized and easily concealed versions, AN/PRC-4 and AN/PRC-6 respectively.
Radio Set SCR-536, the original Walkie Talkie (or Handy Talkie) in use on a beach during WW II.
Note on terminology: The SCR-536 was originally called the "Handie-Talkie" (meaning it could be carried in your hand) while the term "Walkie-Talkie" referred to man-portable backpack units like the SCR-300 (meaning you could walk and talk). Gradually "walkie talkie" came to mean any small, handheld radio, including the SCR-536, usage that is not consistent with the WW II era usage.
Find More Information on the Internet
There are many fine websites that have additional information on this
topic, too many to list here and too many to keep up with as they come and go.
Use this Google web search form to get an up to date report of what's out there.
For good results, try entering this: scr536 or bc611. Then click the Search button.