DRAG DROP
Select the voice gateway trunk interfaces on the left, and drag them to the appropriate columns on the right. All
interfaces will be used. Not all boxes will be filled.
Select and Place:

Answer:

Explanation:
Ear and mouth (E&M), foreign exchange office (FXO), and foreign exchange station (FXS) interfaces are all
analog interfaces. Integrated Services Digital Network (ISDN) Primary Rate Interface (PRI) and channelassociated signaling (CAS) T1 interfaces are digital interfaces.
An E&M interface is used to interconnect private branch exchanges (PBXs) or telephone switches. Because an
E&M interface is typically used as a trunk interface for a PBX, it does not supply ring voltage. In addition, an
E&M interface uses its own signaling for voice transmission and call control.
An FXO interface is typically used to connect an analog device to the public switched telephone network
(PSTN). In addition, if a PBX is configured with an FXS port, the FXO interface on an analog device can
terminate an analog trunk from a PBX. FXO interfaces are commonly found on standard telephones, fax
machines, and analog modems. Thus devices that have FXO interfaces typically connect to the PSTN by using
plain old telephone service (POTS) lines.
An analog trunk from the central office typically originates from an FXS interface on a phone switch. The switch
provides dial tone, ring voltage, and line voltage for the customer site. Because the FXS interface on the phone
switch provides power, it cannot be connected to another FXS interface; instead, the FXS interface must be
connected to a device with an FXO interface, such as an analog telephone or a legacy voice mail system.Cisco
Analog Voice Gateways, such as the VG202 and the VG204, come with FXS ports that enable you to connect
FXO devices, such as corded analog telephones or cordless analog telephone bases, to Cisco Unified
Communications Manager. The VG202 supports up to a maximum of two analog devices. The VG204 supports
up to a maximum of four analog devices.
A PRI T1 circuit uses timedivision multiplexing (TDM) to allocate up to 24 time slots, or channels, that can be
used to transmit voice, video, and data traffic. Time slots 1 through 23 can be used to send data, such as
analog voice? time slot 24 is used for signaling. Each of the 24 channels provides 64 Kbps of bandwidth for a
total data bandwidth of 1.536 Mbps. One framing bit is added to each 192bit frame for an additional 8 Kbps,
bringing the total line bandwidth to 1.544 Mbps. PRI T1 circuits can transmit proprietary PBX signaling
messages by using ISDN signaling.
A T1 circuit is a digital trunk that uses TDM to allocate up to 24 time slots for voice channels. CAS uses aportion of each channel to send signaling information to the central office (CO). By contrast, common-channel
signaling (CCS) devotes an entire channel to signaling information. Although this allocation provides one less
channel for voice, it ensures that the entire bandwidth of each voice channel can be used for transmissions.

https://www.cisco.com/c/en/us/tech/voice/analog-signaling-e-m-did-fxs-fxo/index.html
https://search.cisco.com/search?query=Cisco%20IOS%20Voice%20Port%20Configuration%
20Guide&locale=enUS&tab=Cisco