Because RFL™ and Hubbell® have a policy of continuous product improvement, we reserve the right to change designs and specifications without notice.
2.2.1.1 E1 TIME SLOT USAGE
The specification for the E1 system calls for 32 full-duplex 64 Kbps time slots, numbered 0 to 31,
providing a data rate of 2,048,000 bps, or 2.048 Mbps. Time slot 0 is reserved for system use (framing
information, CRC, etc.) and is not available to the user. This leaves a maximum aggregate payload
capacity of 1.984 Mbps (31 time slots of 64 Kbps each).
Some applications, such as voice communications, require additional data such as ring, on-hook, or
off-hook state to be associated with the payload. This additional information is referred to as signaling.
In E1 systems this signaling information is passed between nodes using Channel Associated Signaling,
or CAS. CAS utilizes time slot 16 to pass the signaling information for all time slots. The E1
specification calls for a multiframe structure within the data located in time slot 16 to allocate the
signaling bits between time slots.
If CAS signaling is used anywhere in a network, it should be used throughout the network, thus
precluding time slot 16 for user data. If CAS is not used in a network, time slot 16 may be used for
payload traffic by selecting Common Channel Signaling (CCS) which will de-select CAS. Note,
however, that this will prevent signaling information from passing between nodes.
The RFL fast reframe uses time slot 30. If fast reframing is required in a network, all nodes should
have fast reframing enabled, and time slot 30 will be reserved. If all nodes have fast reframe disabled,
time slot 30 will be available for user payload data.
RFL recommends using the Network Communications Module (NCM) for network communications
on time slot 31.
Note from the above discussion that an E1 network can have between 28 and 31 time slots available
for user payload depending on the system configuration.
IMUX 2000E1 RFL Electronics Inc.
April 1, 2007 2-3 (973) 334-3100
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