There are many different optical encoders that, while being built around the same principle, are different when it comes to power supply or output signals. 5V is the most widely used in machine tools and measurement machines, where the encoder is connected to a NC or to dedicated electronic boards. The output signals of encoders powered at 5V can be either TTL or line-driver (LD). In TTL encoders the signal is carried by a single wire, meaning that the signals A, B (corresponding to the A and B impulse sequences) phase-shifted by 90° and the Z signal corresponding to the index mark. In LD encoders every signal is carried by a pair of wires in differential mode. The signal wires thus become 6: A, ~A, B, ~B, Z and ~Z. The advantage of TTL encoders is the smaller number of connector wires, while the LD ones are less affected by electrical noise, particularly when using long cables, as in the case of machine tools.

The Sinai TTL-LD converter has been designed for connecting TTL encoders to LD inputs. Apart from interfacing encoders with different input circuits, the TTL-LD converter is employed when needing an high immunity to electrical noise while only having TTL encoders available. Installing a TTL-LD converter, the cable leading from the encoder to the NC will carry LD differential signals, less susceptible to noise. This compact device features sub-d 9 pins M or F. Power for the converter is provided by the cable leading to the encoder, with a maximum draw of 20mA. For NCs or for any other device with a LD encoder input, the TTL-LD converter is completely transparent.