In the good old days there was a danish keyer called the SQUEEZE KEY.
It was almost like yambic B keying but only with one DIT memory. The operators in the Navy and in the army used them, and from one of them, Per OV2V, i learn about this keyer. www.ov2v.dk/
He told me that the operators feel that they could do better and faster CW because of the keying where they could keep the DIT fingers on the paddle, because of the ONLY ONE DIT memory.
Here you can find 2 pdf files with the original instructions.
Here you see the Danish Squeeze Keyer. Picture from OV2V.
Per and I did develop a copy based on the ARDUINO UNO and a very simpel setup.
And here you find the code for the Arduino UNO www.skovholm.com/Squeeze_keyer_v2.ino ( right click on the mouse and save as)
Have a nice time building this keyer ;o)