Quik-Call I, also known as 2+2, is a selective calling method originally used in one-way paging receivers. The "Quik-Call" name is a trademark of Motorola. It sends a pair of tones followed by 50 to 1,000 milliseconds of silence and then a second pair of tones. Decoders look for a valid first tone pair followed by a valid second tone pair within a defined length of time, (a "time window"). For example, a decoder detecting a valid first tone pair might allow up to 2 seconds for a valid second tone pair to be decoded. If no valid second tone is decoded within 2 seconds, the decoder resets and waits for another valid first tone pair. The system is less susceptible to falsing because it employs pairs of tone decoders that must detect valid tone pairs simultaneously.