The Models AM25CK and AM70CK are connector kits which allow the use of SelecTone speaker/amplifiers (1Vrms devices) to be used in any public address system (25 or 70Vrms).

Using these connectors and the 25Vrms output from the 300VSC–1, 300VSC–1044SB, 300SCW–1, 300MB or 300MC SelecTone Command Center creates a true "balanced line" system which will filter all extraneous noise from the audio lines.

Expanding a centrally amplified public address system often requires the addition of another control amplifier. With the appropriate connector kits and SelecTone speaker/amplifiers, the system can easily be expanded, without the costly addition of a central amplifier.

Public address equipment manufacturers do not offer a wide selection of explosion–proof products. Now adding a Class I, Division 1, or Class I, Division 2 device to an existing central PA system is simple; select either a 300X, 300GCX, or 302GCX speaker/amplifier and the appropriate connector kit.

SelecTone typically require a minimum of 18–gauge twisted pair, isolated from the AC line. With an AM series connector kit and the 25Vrms output of the SelecTone control, a balanced line is created which filters induced line noise. This also allows the installer to use smaller gauge wire without the risk of poor intelligibility.

Federal Signal's SelecTone Connector Kits allow existing public address systems to be expanded with SelecTone speaker/amplifiers – no additional central amplifier is required.