A plain-language radio check is the means of requesting and giving a signal strength and readability report for radiotelephony (voice) communications, and is the direct equivalent to the QSA and QRK code used to give the same report in radiotelegraph (Morse code) communications. SINPEMFO code is the voice signal reporting format developed by the ITU in 1959, but sees little use outside of shortwave listeners.
Allied Communications Procedure 125(F), Communication Instructions Radiotelephone Procedure,[1] published by the Combined Communication Electronics Board, defines radiotelephone procedures, and contains the original definitions for many common radio communications procedures, including Procedure Words, radio net operations, etc. Section 611 of ACP 125(F) details how to conduct radio checks using plain language.
The prowords listed below are for use when initiating and answering queries concerning signal strength and readability.
| Proword | Meaning |
|---|---|
| RADIO CHECK | What is my signal strength and readability; how do you hear me? |
| ROGER | I have received your last transmission satisfactorily. |
| NOTHING HEARD | To be used when no reply is received from a called station. |
| Proword | Meaning |
|---|---|
| LOUD | Your signal is very strong. |
| GOOD | Your signal strength is good. |
| WEAK | Your signal strength is weak. |
| VERY WEAK | Your signal strength is very weak. |
| FADING | At times your signal strength fades to such an extent that continuous reception cannot be relied upon. |
| Proword | Meaning |
|---|---|
| CLEAR | The quality of your transmission is excellent. |
| READABLE | The quality of your transmission is satisfactory. |
| UNREADABLE | The quality of your transmission is so bad that I cannot read you. |
| DISTORTED | Having trouble reading you due to interference. |
| WITH INTERFERENCE | Having trouble reading you due to interference. |
| INTERMITTENT | Having trouble reading you because your signal is intermittent. |
One of these reports, "LOUD AND CLEAR", is commonly used in television shows, movies, literature, and by radio operators, commonly without knowing the source or the rest of the standard reports (hence the much-reduced frequency with which the other combinations are used). For example:
The omission of comment on signal strength and readability, by responding only with the proword ROGER, is understood to mean that reception is LOUD AND CLEAR. If reception is other than loud and clear, it must be described with the appropriate prowords.
Reports such as "five by five", "four by four", etc., will not be used to indicate strength and quality of reception.