APPENDIX D
Dealer Desks
(Hoot ‘n Holler
Boxes, Hybrids and
Switched
Telephones)
A typical dealer desk application is shown in the following diagram. The
design of these vary in detail. The Selector switch selects between phone
and hoot 'n holler box. Note that two hybrids may exist in a single voice
circuit.
PHONE
HYBRID
(4-WIRE)
(2-WIRE)
MICROPHONE
SPEAKER BOX
(HOOT 'N HOLLER CKT)
HYBRID
SELECTOR
SWITCH
HYBRID
CELP/MUX
NETWORK
(2-W)
(4-W)
+
036R480DC
CHECK LIST FOR HOOT ‘N HOLLER CIRCUITS
•
Compile an end-to-end Loss Plan for the whole network.
•
Adjust levels with real loads in both directions for both telephone and
microphone circuits. Use dBm meter in “Bridge’’ or “High
Impedance’’ mode. Add only enough gain to compensate for the hybrid
insertion losses.
•
Measure the Echo Return Loss (ERL) at each CELP.
•
Calculate each CELP’s CODEC Echo Return Loss from the measured
ERL and CELP transmit and receive gain values. Check for compli-
ance with the 6 dB rule.
Conference
Circuits (with
Tandeming via
Analog Bridge
Circuits)
The Analog Bridging Circuits are the key to conferencing and tandem-
ing 4-wire voice circuits. The transmit side of each port transmits the
summed value of each of the receive inputs from the other three ports. All
ports are identical in design. CELP circuits may be used in either the
link circuits or to connect stations to the Bridges. If voice quality is an
issue for multitandeming situations, you may consider replacing one of
more of the inter-bridge link circuits with a PCM or ADPCM circuit.
D-9
