The FS1000A is basic RF transmitter than comes in at least two frequencies, 315 MHz and 433.92 MHz.

None of the devices tested are particularly well tuned and tuning also alters somewhat when attaching an antenna. The Gqrx image shown is one example FS1000A at 433.863 MHz with a 17cm antenna. On the same plot we can see a faint signal from another device which is exactly 433.92 MHz.

These devices work fine using 3V3 or 5V for VCC and the digital input named DATA, ADAT or ATAD works equally well at 3V3 for 3V3 VCC or 5V VCC.

To complement the FS1000A, the RF-5V (or equivalent) exists. This receiver module works okay at 3V3 for short distances but is rated for 5V operation which is needed for longer distances. It would appear that 5V is required to operate the AGC circuit on the board. The AGC can produce high levels of noise on the output when no signal is broadcast from the FS1000A.

The second photo here shows the receiver. In this setup the output is fed into a cheap USB sound card whilst the FS1000A sends an AFSK signal. On the receiver host minimodem is used to decode the message reliably.