Since the early days of air travel there has been a requirement for airlines to stay in two-way radio communication with their aircraft. Quickly the amount of voice communication on the designated "party line" radio frequency became so great it presented an operational problem. In response, a selective calling system (SELCAL) was developed that relieved flight crews from having to continuously monitor the network radio for incoming messages while ensuring the rapid and reliable access necessary to meet operational communications regulations.

Today, ARINC and other communication networks allow airline and business aircraft operators to stay in communication with their dispatch office over entire routes. The SELCAL system consists of a ground-based SELCAL encoder and a VHF or HF communication system and the airborne decoder. Each aircraft's "SELCAL decoder" is assigned a unique code. The airborne SELCAL decoder is connected to the aircraft's VHF and HF radios. When the aircraft is called, an aural alert is received and the active radio is identified on the cockpit annunciator panel, signaling the flight crew to monitor the company radio frequency.

Avtech's range of SELCAL products includes ground-based desk-mounted encoders; ramp testers with VHF and HF (RF) outputs; standard ARINC 714 SELCALs; and space-saving, panel-mounted SELCALs. Older aircraft also benefit from Avtech's legacy products catering to the ARINC 531 standard.