... therefore, signaling is sent above the 3400 Hz (and below 4000 Hz). This is known as out-of-band signaling and is used in R2 for supervisory signaling. Unlike with in-band signaling, no contention ... implemented using the following related systems: • Bell Systems MF, R2, R1, and C5. • Single-frequency (SF) in-band and out-of-band signaling • Robbed bit signaling The following sections discuss ... frequency bandwidth, only signaling or user traffic can be present at any one time. Therefore, in-band signaling is restricted to setting up and clearing calls down only because signaling is not possible...