Signaling Equipment

TM 11-5895-1012-10

ate such that if any one user transmits a message, it is

received by all others in the group. The network allows

any user to transmit as long as only one station is

transmitting at any particular moment. The hubbing

a considerable number of FDM terminals in use in the

repeater may be used as the interface device between a

DCS which do not utilize the standard parameters.

Send Only device and several receiving terminals.

When interconnection at the group or supergroup level

d. Passive Peak Limiter. This unit is used to auto-

is required between this nonstandard equipment or

mat&By prevent system overload causes by excessive

standard to nonstandard equipment special condition-

transmission levels from the user equipment This

ing equipment is required between the multiplexers

equipment is located on the equipment side of the

for the purpose of level compatibility and impedance

Equal Level Batch Bay within the conditioning string

matching. This conditioning equipment is connected

on audio channels.

in the same manner circuit conditioning equipment

e. 6-Way 4-Wire Bridge. This unit provides a con-

would be connected on the circuit level.

ferencing capability for 6 each 4-wire telephone cir-

c. Nonstandard multiplex equipment in use in the

cuits.

DCS generally does not utilize the same pilot fre-

quency as that used in the standard parameter (104.08

2-34. Signaling Equipment

kHz). When multiplex utilizing different pilot fre-

The signaling equipment in the Technical Control

quencies must be interfaced at group or supergroup

Facility provides the means of interfacing ringing and

levels, pilot conversion is required. This process is re-

dial pulse signaling between two different cross-con-

ferred to as pilot stop and reinjection. Suitable equip

nected channels. The equipment is also used to change

ment must be provided which will stop the unwanted

the signal from out-of-band signaling to in-band sig-

pilot frequency and permit insertion of the required

naling. Various types of signaling equipment is dis-

pilot frequency. Equipment which perform these func-

cussed below.

tions are commonly called pilot stop and reinjection

a. Single Frequency Signaling Units (SFSU). This

filters, and are especially designed for interface at the

equipment is used when it is necessary to convert from

pilot frequencies of the multiplex terminals.

E&M signaling to in-band 2600 Hz or 1600 Hz signal-

2-33. Other Conditioning Equipment

ing or in-band to E&M signaling. The SFSU transmit

section converts dc-dialing or supervisory signals pres-

Technical Control Facility personnel will be required

ent on the M-lead into an amplitude-modulated tone

to be familiar with the operational and technical char-

for transmission over voice frequency channels. The

acteristics of other ancillary equipment which may be

SFSU receive section converts received amplitude

required to assure proper operation but which are not

modulated tones into dc-dialing or supervisory signals

usually referred to as conditioning equipment.

on the E-lead. The state of the E&M leads may be

a. Four to Two-Wire Terminating Sets. The four to

grounded, +48 vdc, or open circuited. The normal

two-wire terminating set is used between a two wire

VF channel and a four-wire VF channel. It converts

E&M logic is as follows:

`the two wires used for transmit-receive to two wires

for transmit and two wires for receive. Usually the ter-

minating sets also provide impedance matching facil-

ities, enabling 600-ohm 4-wire circuits to be con-

b. E&M/Loop Converter (E&M to Dc). The dial loop

nected to 600- or 900-ohm 2-wire circuits.

to the E&M converter provides complete access be

b. 600-Ohm Terminations. The normal terminated

tween a central office and a dial user instrument over a

impedance of lines used in telephone work is 600

voice frequency carrier channel. There are two ver-

ohms, although some 900 ohm terminations may be

sions of this unit as follows:

used. When the equipment normally used to provide

(1) Central Office Dial Loop to E&M Converter.

proper termination is removed, the Technical Control-

This unit receives 20 Hz from the central office and

ler must have available a rapid method of terminating

converts it to an M-lead seizure for input to an SFSU

lines so that any test measurement made on the line

in the outgoing direction, and presents a closed loop to

will be accurate. A device in common use in Technical

the central office when the E-lead from the SFSU in-

Control Facilities is a terminating resistor which is

dicates an incoming call.

usually a noninductive resistor of the proper value

(2) User Dial Loop to E&M Converter. This unit

wired across plugs of the same type as those used at

recognizes a closed loop when the user goes off-hook

the patch panels.

and indicates seizure to the M-lead and converts dial

c. Data Conferencing Network. This device (also

pulses to M-lead pulsing of the SFSU. When a call is

known as a Technical Control Facility Hubbing Re-

incoming to the user the E-lead causes a 20 Hz ringing

pester) enables a predetermined group of users to oper-

signal to be sent to the end instrument.

2-37