The 240 can execute programs from an optional magnetic disk or paper tape, for example as installed in the S-3130 testing station.
The 240 is essentially a 192 bit shift register, generally organized in 4 bit characters. Alone, it is able to completely control the plug-ins of a 568, and the type 230 Read-Out Unit. The output can be expanded to up to 576 bits with the addition of 2 Type R250 Program Control Units, to allow it to control other instruments such as the R116 or R293 pulse generators. With just one 240, there are 14 spare bits that can be used for controlling other components.
The 240 is able to advance sequentially through program steps stored on either the paper tape or disk unit, with basic program control flow (stop or branch) available, driven by the status of the limit indicators on the 230. Each test can be programmed to occur once or twice, in order to minimize the chance of errors due to transients. Each test contains the address of the next test, and a branch status simply adds one to that address. Through J302, addressing functions can be monitored and controlled; presumably more advanced program flow control could be implemented using a computer.