Section 365-336-202
5
4.4
2713Hz Tone-Activated Loopback
The 3653–36 provides tone-operated loopback toward the digital facility. A continuous 2713Hz loopback control
signal applied from the far end for a minimum of 2.2 seconds and then removed will result in the operation and
latching of the LB RELAY and the illumination of the front-panel LB LED. While operated, the LB RELAY will per-
form the following functions:
Opens the 4W port to the 4W equipment preventing transmission.
Loops all voice-band signals from the RCV output to the XMT path, enabling all active components to
be verified.
The EQUAL LEVEL LOOPBACK circuit provides prescription level adjustment of +31.5dB in 0.5dB steps to
match the RCV output to the XMT path input.
Loopback release is accomplished by the reapplication of 2713Hz tone (for a minimum of 1.1 seconds) to the
3653–36. After the 2713Hz tone has been received, the LB RELAY releases and the LB LED extinguishes, end-
ing the loopback condition.
The loopback control circuit provides several control options as selected by switch S8. The tone activated loop-
back feature can be disabled or enabled. In addition, when the unit has been looped via a 2713 Hz tone, the cir-
cuit can be optioned to have a 4-min, 20-min, automatic release, or no timeout.
4.5
Manual Loopback
The 3653–36 can be manually placed in the loopback mode by momentarily operating the front-panel MLB push-
button switch (S9). The module will remain in the manual loopback mode regardless of the settings of S8. To re-
lease the manual loopback mode, the MLB switch is again momentarily operated.
4.6
7 5/6-Bit or 8-Bit (Encoding & Decoding)
The 3653–36 provides 7 5/6-bit or 8-bit encoding and decoding schemes for the transmit and receive paths to/
from the facility. The 7 5/6-bit encoding/decoding scheme provides for end-to-end compatibility with E&M chan-
nel units. In this scheme a constant off-hook (logic 1) is transmitted on the A+B signaling bits to the far end.
The full 8-bit encoding/decoding scheme provides a greater signal-to-noise ratio than the 7 5/6-bit scheme and
does not transmit an off-hook signal to the far end.
5.
MOUNTING
The 3653–36 mounts in one channel unit slot of a 360/363 D4 terminal. The 3653–36 is equipped with an insert/
eject lever in the form of a hinged front panel which ensures a positive connection of the channel unit’s card-edge
connector to the backplane connector when the unit is installed. The insert/eject lever also facilitates removal of
the unit.
Installation and removal of modules should be done with care. Do not force a module into place. If
excessive resistance is encountered while installing a module, remove the module and check the
card guides and connector to verify proper alignment and the absence of foreign material.
CAUTION
Step
Action
1.
Align the channel unit with the appropriate card-guided slot of the terminal.
2.
Slide the unit into the slot with the hinged front panel in a horizontal (up) position.
3.
When the top portion of the hinged front panel is under the front lip of the terminal, push down on the
front panel until it is in the vertical position. The channel unit’s card-edge connector will begin to make
contact with the inner portion of the backplane connector.
4.
Continue applying light pressure onto the bottom edge of the front panel until the unit snaps into place.