2248 CHAPTER 131: VOICE SUBSCRIBER L INE CONFIGURATION3 Use the vi-card busy-tone-detect command in voice view to start the detection.To seize the busy tone signal sent by PBX B, you are recommended to run theabove command 2 seconds after on-hook.4 (The console terminal displays "Begin to autodetect busy-tone, it will take about12 seconds, please wait...", which indicates that the busy tone detection is inprogress. After the detection, the terminal displays "Auto-detect busy-tonesucceeded!", which indicates that the detection succeeded.) Use the savecommand to save the detected busy tone parameters.5 Repeat step 2 to verify whether the automatic busy tone detection succeeded. Ifsucceeded, Telephone A will automatically be disconnected and Telephone B willhear a "Clatter" sound after PBX B plays busy tones to Router A for 4 seconds.E&M Voice SubscriberLineE&M Interface An ear & mouth or receive & transmit (E&M) interface uses an RJ-48 telephonecable to connect a PBX. The PBX sends signals on the M (M represents mouth) lineand receives signals on the E (E represents ear) line. Viewed from a voice router,the router receives M signals from the PBX and sends E signals to the PBX. Thedevice with an E&M interface can be connected to another device with the sameinterface.When analog E&M is applied in VoIP communication, 2 or 4 voice wires can beused. Besides, there are 2 or 4 signaling wires. Therefore, 4-wire analog E&Mactually has 6 wires. The 2-wire mode provides full duplex voice transmission andvoice is transmitted in two directions on the two wires. The 4-wire mode isequivalent to the simplex mode and every two wires are responsible for the voicetransmission in one direction.Start Mode An E&M interface supports E&M signaling and divides each voice connection intotrunk circuit side and signaling unit side (similar to DCE and DTE).An E&M interface provides on-hook/off-hook signals and minimizes theinterference. Because an E&M interface does not provide any dial tone, one of thefollowing three signaling technologies is used to start dialing:■ Immediate start: In this mode, the caller picks up the phone, and some timelater, the dialed number is sent to the called side. During this period, whetherthe called side has been ready for receiving the called number is not checked.After the called information is received, the callee can pick up the phone toanswer the call.Figure 652 Immediate start modeCallingside (E/M)CalledPick up the phone, requesting for serviceSend the called numberConversationConversationPick up the phone to answerHang upCallingside (E/M)Calledside (M/E)Send the called numberConversationConversationCallingside (E/M)CalledPick up the phone, requesting for serviceSend the called numberConversationConversationPick up the phone to answerCallingside (E/M)Calledside (M/E)Send the called numberConversationConversationHang up
