Digital Data Circuits

TM 11-5895-1012-10

the Dc Primary Patch Bay. The signal from the Dc Pri-

pulse link repeater may be required far transposition

mary Patch Bay, if nonstandard or if isolation is re-

of the E&M leads. Level control is maintained, as re-

quired, is converted to standard low-level and then ac-

quired, by pads and amplifiers as indicated.

cesses the Dc Equal Level Patch Bay.

x. Four-Wire Entrance Toll Cable (Fig. 2-8

This circuit is required for interconnection at the Pri-

(2) Digital Data User-Access Circuits Via VF

Transmission Mode. All user-access lines entering the

mary Patch Bay with any long distance physical com-

TCF by way of VF transmission mode is treated as a

mercial toll circuit. Level adjustment using pads and

VF circuit until converted to standard polar dc signals.

amplifiers is located between the Primary and Equal

The standard low-level polar dc then accesses the Dc

Level Patch Bays.

y. Four-Wire Connections to High Frequency Radio

Equal Level Patch Bay. At this point the dc circuit is

either looped back to the local user or reconverted to

Systems (fig. 2-8

). The remote high frequency

radio transmitter and receiver sites may access the

voice frequency for transmission over long haul trans-

Technical Control Facility by either microwave radio

mission media.

or cable intersite links. Since the send and receive

(3) Technical Control Access Digital Data Cir-

channels are one-way and receiving combining is used

cuits. All TCF dc circuits (teletype orderwires, report+

on the carrier telegraph system, all channels access the

ing circuits, etc.) appear directly at the Dc Equal Level

Primary Patch Bay regardless of the intersite trans-

Patch Bay.

mission media. Similar connections are made for these

(4) High Speed Data. All high speed (above 1200

baud) dc circuits except those requiring coaxial type

channels with pads and amplifiers for level adjust-

ment, before the circuits access the Equal Level Patch

wiring access the Dc Equal Level Patch Bay directly

Bay.

without prior access through the Digital Line Interface

Unit. All high speed dc line outputs and modems pm

2-18. Digital Data Circuits

vide the standard low-level polar signal.

Existing digital dc circuits consist of a wide variety of

c. Timing, Control, and Alarm Circuits. Provisions

modulation rates, modes of operation, unit codes, and

are made on the Dc Equal Level Patch Bay for patch-

ing and testing of all timing, control, and alarm cir-

circuit configurations. The variety of circuits and vari-

ous equipment arrangements at the user end has

cuits.

caused nonstandardization of dc Technical Control

d. Testing of Dc Signals. All dc circuits appear at

Facilities.

the Dc Equal Level Patch Bay. Dc signals which

a. Signal Levels. All dc circuits appearing at the dc

appear at the Dc Primary Patch Bay will differ in cod-

Equal Level Patch Bay are configured for low-level

ing schemes and baud rates. Testing of all dc circuits

polar operation.

will be performed on a high impedance basis. Signal

(1) Only low-level operation is used within the

levels applied to the high impedance test equipment in

black patch, test, or conditioning equipment area with-

all cases are equal no matter what the coding scheme

in the TCF. Only low-level operation is used within a

or baud rate.

red equipment area when such an area is required to

2-19. Wideband Facilities

support the TCF. All teletype and data end equipment

(fig. 2-6)

used within the Technical Control Facility is config-

ured for low-level operation in order to provide flex-

a. General. Facilities for monitoring, testing, and

ibility during equipment substitution and to facilitate

patching of wideband circuits, multiplex groups,

conversion to encrypted operation at a later date.

supergroups, and basebands are provided at stations

(2) Unencrypted data orderwire and reporting cir-

where required as outlined below. Wideband jack-

cuits may be required at some locations. These circuits

fields, in bays separate from VF and dc jackfields are

are intended for encrypted service at a later date and

provided for this purpose.

are configured and routed in-station so that instal-

(1) Wideband circuit monitoring and testing

lation of the cryptodevice will not require major rewir-

facilities are provided at all stations which control

ing of the circuit.

such stations. At stations where alternate routes or

b. Basic User Circuits. The total user requirements

spare equipment for such circuits are available, patch-

are reducible to four basic types, allowing simplicity

ing facilities to permit reroute or restoral is also in-

and standardization, at the digital dc patch panel and

cluded within the TCF.

improve efficiency. The four basic types of user-access

(2) Group, supergroup, and baseband monitoring,

circuits described below are shown in figure 2-9.

testing, and patching facilities are provided at all sta-

(1) Digital Data User-Access Circuits Via Dc

tions having more than two multiplex link terminals,

Transmission Mode. All user-access lines entering the

and are sometimes provided at smaller stations to

Technical Control Facility by way of the dc transmis-

meet special requirements. Normally, at stations hav-

sion mode makes an appearance on the dc portion of

ing only one or two multiplex link terminals, the jack

2-24