To convert the audio signal between receiver and PC, a very simple comparator type interface is used. This kind of interface (Hamcomm-type) circuit is used by several other RTTY and SSTV programs. It connected to the serial interface (COM-1..COM-8). Due to the digital signal processing, GSHPC achieves a very high image quality, sharpness and synchonisation stability.

* Pervisell Ltd (UK). See also the Homepage of Pervisell Ltd.
* HAMCOM or compatible (siehe text below)
* BP-2/BP-2M  (Tigertronics)
* Home made

The more important requirement is, that the square wawe signal is 100% symmetrical when receiving a not modulated signal.. Some modems use simple 741 op-circuit having a big offset error, causing unsymmetrical output signal. It causes some noise (moire) in the received image. The easiest way to eliminate it, to exchange the 741 to the pin-compatible CMOS type (e.g. CA-3140).