Voice Frequency Circuits

TM 11-5895-1012-10

not included in the following list. A description of each

date a wide range of data rates to produce a single

circuit follows in the paragraph indicated.

serial stream of information, with its associated tim-

(1) Two-wire voice user with 20 Hertz signalling

ing.

j. Pulse Code Modulation Equipment (PCM). The

(para c below).

(2) Two-wire voice user with loop signalling (para

pulse axle modulation equipment normally accepts the

d below).

analog signal (the modulating signal) and samples it at

(3) Two-wire voice user with E&M signalling (para

a predetermined rate. The sample is then quantized

e below).

and coded so that each element of information consists

(4) Two-wire voice user with standard integral sig-

of differing numbers of pulses (marks and spaces).

This equipment generally uses an eight bit sample

nalling (para f below).

(6) Four-wire user with standard integral signal-

rate.

k. Modems.

ling (para g below).

(6) Four-wire user with 20 Hertz signalling (para h

(1) Digital Modems (VF). This is a modem which is

below).

used to convert direct current signals appearing on the

(7) Four-wire user with loop signalling (para i be-

digital patch bay to the analog form for appearance on

low).

the equal level patch bay. This equipment requires a

(8) Four-wire data user cable to TCF (para j be-

nominal bandwidth of 4 kHz

low).

(2) Special Digital Modems (Group). Input to this

(9) Two-wire or four-wire voice user using non-

modem is in digital form from the digital patch bay.

standard in-band signalling (nonstandard signalling

Its output is analog form and appears on the group

unit at user terminal) (para k below).

patch bay in the standard frequency division multi-

(10) Four-wire user with DX signalling (para l be-

plexed group frequency bandwidth of 60 to 108 kHz.

low).

(3) Special Modem (Supergroup). Input to this mo-

dem is in digital form from the wideband user/switch

(11) Four-wire PBX trunk to AUTOVON (PBX

cable to TCF) (para m below).

or TDM. Its output in analog form appears on the su-

pergroup portion of the coaxial patch bay in the stand-

(12) Four-wire data user with DX signalling (para

ard FDM supergroup frequency bandwidth of 312 to

n below).

(13) Two-wire PBX cable access line (two to four

552 kHz.

wire conversion at PBX) to local AUTOVON switch

2-17. Voice Frequency Circuits

(para o below).

a. General. All voice frequency (vf) users including

(14) Four-wire AUTOVON subscriber telephone

AUTOVON, AUTODIN, and AUTOSEVOCOM

cable to TCF (loop resistance less than 700 ohms) (para

switches, communications centers, PABX's, local

p below).

switchboards and tactical multiplex equipment access

(15) Four-wire AUTOVON circuit (remote two-

the TCF by way of the Primary Patch Bay. Four-wire

wire PBX subscribers) (para q below).

fixed station multiplex equipment utilizing 2600

(16) Four-wire AUTOVON special grade circuits

Hertz signaling access the TCF by way of the Equal

(AUTOVON subscribers (data) and inter-switch

Level Patch Bay. All conditioning and signalling

trunks) (para r below).

equipment required to achieve compatibility between

(17) Four-wire AUTOVON voice grade circuits

users and the transmission media is electrically con-

(para s below).

nected between the Equal Level Patch Bay and the Pri-

(18) Voice and telegraph users connected to High

mary Patch Bay. The Primary Patch Bay terminates 2,

Frequency radio transmission media (pars t below).

4, 6, or 8 wire user circuits. The Equal Level Patch Bay

(19) Four-wire voice frequency carrier telegraph

serves at the principal point of interface and restora-

(para u below).

tion in the Technical Control Facility. Circuits appear-

(20) Fixed station multiplex interconnection (para

ing at the Equal Level Patch Bay appear as 4-wire bal-

v below).

anced pair circuits (AUTOVON switch circuits having

(21) Non-DCS multiplexer user to DCS user on

Pilot Make Busy capability appear as five-wire cir-

base, or using DCS transmission media (para w below).

cuits). The Equal Level Patch Bay is the zero (0) test

(22) Four-wire entrance toll cable (para x below).

level point in the station, that is, OdBr send and re-

(23) Four-wire connections to High Frequency ra-

ceive. DCS standard supervisory signals appear as

dio systems (para y below).

2600 Hertz tones at the Equal Level Patch Bay.

c. Two- Wire Voice User With 20 Hertz Signalling

b. Circuit Descriptions. The following is a list of the

(fig. 2-8

). The users for this circuit are either a

various types of voice frequency circuits which may be

two-wire switchboard or an individual two-wire user

commonly found appearing in the Technical Control

using 20 Hertz ringing source. This circuit provides

Facility. A TCF may service other circuits which are

echo suppression and control in order to minimize

2-15